Growth of sorghum and maize was analysed to determine the pattern of physiological growth parameters and its effect on yield components, dry matter accumulation and nutrients quality of the plants. The experimental fields were laid down as a randomized block with 4 replications at Livestock Experiment Station in Suweon during 1984-1986. The results obtained are summarized as follows: 1. Assimilable leaf area was shown to have a great enlargement at the growing point differentiation both in sorghum and maize. Maximum LAI was found at heading stage with a value of 14.98 for sorghum and 6.02 ㎡/㎡ for maize. 2. Net assimilation rate (NAR) was decreased as the vegetative development progressed. Dense population increased LAI, but NAR was negatively associated with plant population. Mean NAR in the whole vegetative periods were 0.79 in maize and 0.50 ㎎/㎠. day in sorghum. 3. Absolute growth rate (Abs. GR) showed linear respones to assimilable leaf area. The highest Abs.GR was found at heading stage, when the leaf area reached maximum size. Maximum dry matter yields of sorghum and maize were 2353 at soft dough and 2037 ㎏/10a at maturity, respectively. 4. Concentrations of crude protein, crude fat and cyanogenic glycosides were positively associated with leaf weight ratio and specific leaf area, while N-free extracts and nonstructural carbohydrates were negatively associated(P◎0.1%).