To explore drought resistance of maize inbred lines, based on leaf photosynthetic parameters at silking stage, we treated 51 maize inbred lines with drought stress at silking stage in Humochuanpingyuanguanqu and Hetaopingyuanguanqu in 2012 and 2013 to analyze response of leaf photosynthetic parameters to drought stress and the relationship between photosynthetic parameters and drought tolerance. The result indicated that at silking stage, no matter under drought and the condition of irrigation, Pn, Tr, Gs, Ci, Fv/Fm, ΦPSII, and SPAD had a significant and positive correlation with drought resistance coefficient, WUE had a significant and negative correlation with it, while qN and qP had no correlation with it. Stepwise regression analysis on the eight leaf photosynthetic parameters above showed that Pn, WUE, Fv/Fm, ΦPSII, and SPAD significantly correlated with drought resistance coefficient at P < 0.01. Pn, WUE and SPAD directly contributed to drought resistance coefficient, while Fv/Fm and ΦPSII contributed indirectly. Thirty-two maize inbred lines were classified into three groups based on different drought resistance, group 1 with the highest drought resistance contained eight inbred lines (H201, H21, Ying 64, Ji 842, Zao 49, Ji 8415, Dong 46, and Shen 137), group 2 with the higher drought resistance contained fifteen lines and group 3 with the lowest drought resistance contained nine lines. The grouping result was consistant with that of yield classification.Therefore, at silking stage, Pn, WUE, Fv/Fm, ΦPSII, SPAD, and drought resistance coefficient can be used as drought resistance evaluation indexes established for the three groups of maize inbred lines. Regression relationship was between Pn, WUE, Fv/Fm, ΦPSII, SPAD, and drought resistance coefficient at silking stage, and the threshold values were confirmed.