To clarify the irrigation strategy for improving yield and its components, the relationship among precipitation, irrigation, yield, and its components was systemically studied under different rainfall conditions. In this experiment, Jimai 585 used as the experimental materials, and five irrigation treatments including W0 (rain fed), W1 (jointing), W2 (jointing, flowering), W3 (jointing, flowering, filling), and W4 (overwintering, jointing, flowering, filling) in the wheat season were set up from 2010 to 2017. The results were as follows: (1) wheat grain yield varied from 6400 to 6800 kg hm-2 under different irrigation treatment in most rainfall years, and spike numbers was positively correlated with grain yield (r = 0.860*), the grain yield, grain numbers per spike, and thousand grain weight increased with the increase of irrigation amount, however, the yield increase rate decreased with each additional water (from 13.8% to 1.7%). (2) There was no obvious correlation between the total precipitation and stage precipitation and grain yield, but the impact of total precipitation on the thousand grain weight was higher than the other factors. Under the conditions of W0 and W1, the effect of total precipitation on the numbers per spike was greater than spike numbers, and vice versa after increasing irrigation. At the same time, the grain numbers per spike was significantly positively correlated with the precipitation before jointing, and the correlation between the grain numbers per spike and the precipitation from February 1 to jointing under W0 was greater than that from sowing to jointing, but it decreased with the increase of irrigation amount. With the exception of the correlation between W4 irrigation and grain numbers per spike and thousand grain weight was higher than that of precipitation, the correlation between two factors and precipitation was higher under W1-W3 conditions, which indicating that irrigation alleviate the adverse effect of insufficient precipitation on grain number per spike. (3) The number of grains per spike and thousand grain weight were the highest in a rainfall year characterized with more precipitation at early growth stages and less precipitation at later growth stages (precipitation before and after jointing 88.2 mm + 29 mm), and the highest yield was observed under 3 irrigation times, and there was no significant difference between 3 irrigation times and 2 irrigation times. In years characterized balanced rainfall (precipitation before and after jointing < 60 mm, 30-80 mm), lower and relatively stable yield and its component appeared, and the grain numbers per spike and thousand grain weight increased slightly after irrigation, but the difference in grain yield between 2 and 3 irrigation times was significant (yield increase rate: 10.5% and 22.9%) (the rainfall after jointing < 36 mm). In year characterized with less precipitation at early growth stages and more precipitation at later growth stages in (precipitation before and after jointing < 25 mm, 40 to 90 mm), the maximum grain number per spike increased by 1.5 to 7.1 grains when irrigation increased, and the grain yield of irrigation 3 times was 13.4% higher than that of irrigation 2 times when inadequate effective rainfall happened in April. In conclusion, when the precipitation before jointing was less than 60 mm (especially less than 25 mm), irrigation at jointing had an obvious effect on the increase of grain number per spike, 3 times irrigation promoted grain yield when the precipitation after jointing is less than 36 mm in a relatively balanced rainfall year type and no sufficient effective rainfall in April in years characterized with less precipitation at early stages and more precipitation at late stages, and irrigation 2 times was suggested to achieve the maximum grain yield in other rainfall years.
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