A field experiment was conducted on maize-mungbean intercropping to assess the yield advantage from the viewpoint of growth process. Three maize densities (75×50, 75×30, 75×15cm^2) were intercropped with mungbean one row between maize rows. Intercropping did not affect the maize yield, but the yields of mungbean were greatly affected. The maximum and minimum yields of mungbean were obtained in a mungbean monoculture plot and mungbean intercropped with a high-density maize plot, respectively. The leaf photosynthetic rate of maize in different plots was insignificant. That of mungbean, however, was significantly affected, and it decreased under the higher density plot. The total dry matter production in per unit area increased due to intercropping. The crop growth rate (CPR) and net assimilation rate (NAR) of maize were highest in the low-density plot and total the CGR and NAR were also highest in the low-density plot at later stages of growth. Land equivalent ratios (LER) were higher than 1.0 in all intercrop plots and crop performance ratio (CPR) was higher than 1.0 only in low-density plot. The highest LER (1.79) and CPR (1.23) were observed in the low-density plot.