To understand the molecular mechanism of maize heterosis, differential gene expression patterns in functional leaves between 10 maize inbreds and 38 hybrids at spikelet differentiation stage were analyzed by using cDNA-AFLP. The correlation analysis of various differential gene expression patterns with the performance and heterosis of main maize agronomic traits was carried out. The main results are as follows: (1) There are differential gene expression patterns in quality and quantity between hybrids and their parents. The differential expression patterns in quality include: bands expressed only in one parent, bands expressed only in both parents, bands expressed only in one parent and F1, bands expressed only in F1. (2) At spikelet differentiation stage, there are large variations among different hybrids for the same differentially expressed patterns. In general from mean data, there were 25.22% bands expressed only in F1, 21.46% bands expressed in one parent and F1, 8.27% bands expressed only in both parents and 33.49% bands expressed only in one parent. (3) For bands expressed only in one parent, significant positive correlation was detected with the relationship to the performance of plant height. For bands expressed only in both parents, significant negative correlation was detected with the relationship to the heterosis of ear diameter. For bands expressed only in one parent and F1, significant negative correlations were detected with the relationships to the heterosis of rows per ear and seed weight per ear. However, for bands expressed only in F1, and for bands only in two parents or only in F1, no significant correlation was detected with the relationship to the performance and heterosis of all agronomic traits.