The effect lf different sowing seasons on the kernel protein and fat content and their total content was studied by sowing 24 southern spring soybean varieties or lines in spring and autumn.The results showed that there existed significant (at 1% level)difference in kernel protein and fat content and their total content between spring and autumn sowing seasons;for protein content,there was a positive correlation(significant at 1% level) to the daily mean,maximun and minimum/temperature from seeding emerging to flowering stage,but a negative correlation(significant at 5% or 1% level)to those from flowering to ripening stage;for fat content,it was just the opplsite.Therefore,in Hunan sowing in autumn season is favorable to the formation of protein while sowing in spring is favorable to the formationg of fat,which results in a higher protein content in autumn sowing season but a higher fat content in spring sowing season.Sown in autumn,the total content of protein and fat in the tested varieties or lines was 59.96% on average,3.08% lower than that sown an spring.