Abstract: The research results showed that among the factors of grain yield component of wheat in annual three- crop system, the panicle number per unit and the grain number per panicle appeared to be the most obvious variation, which contributed the greatest to the increase of grain yield.The tillering duration of wheat in annual three- crop system was short.Thus the panicle number mainly depended on main stem heads.The wheat showed more spikelet differentiation, but 70%～80%of them degenerated, therefore the potentiality of getting large- panicle was on decreasing the degen-eration of spileket.