Maize photosynthate basically stops its allocation to nutrition organs when the leaf area index reaches its maximum, which is a sign of maize entering the reproductive stage. Based on the field experiment data of spring maize with different maize varieties from Jinzhou Agricultural Ecosystem Research Station during 2005-2011, this paper found that spring maize maximum leaf area index appeared around 2 weeks after the silking stage, and put forward an indicator for determining the maximum leaf area index of spring maize, that is, ≥10℃ effective accumulated temperature from the seeding to the maximum leaf area index is 1085.3 ℃·d and (or) 1010.4 ℃·d from the emergence to the maximum leaf area index. Thus,a universal dynamic model of spring maize relative leaf area index was developed on the basis of modified logistic equation. The results would provide reference for accurate simulation of leaf growth and photosynthate allocation of spring maize.