Two winter wheat(Triticum aestivum L.)cultivars, large-spike type Yumai66 and small-spike type Yumai49, were used to study the activities of enzymes involved in starch synthesis in the kernel during grain filling. Starch accumulated faster in the kernel of Yumai49 than Yumai66 up to 25 d after anthesis, thereafter starch accumulated faster in the kernel of Yumai66. Starch accumulation in Yumai66 peaked at 20 -25 d after anthesis, while in Yumai49 starch accumulation peaked at 15 -20 d after anthesis and 25 -30 d after anthesis. The first peak was much higher than that of the second. Sucrose content and sucrose synthase activity peaked at 20 and 15 d after anthesis in Yumai66 and Yumai49, respectively. The sucrose content and sucrose synthase activity in Yumai66 were higher than that in Yumai49 during grain filling. ADP-glucose pyro-phosphorylase and starch branching enzyme activity in the kernel of Yumai66 peaked at 20 d after anthesis. while soluble starch synthase activity peaked at 10 and 20 d after Two winter wheat (Triticum aestivum L.) cultivars, large-spike type Yumai 66 and small-spike type Yumai 49, were used to study the activities of enzymes involved in starch synthesis in the kernel during grain filling. Starch accumulated faster in the kernel of Yumai 49 than Yumai66 up to 25 d after anthesis, followed by accumulation of in starch in Yumai 66. Starch accumulation in Yumai 66 peaked at 20-25 d after anthesis, while in Yumai49 starch accumulation peak at 15-20 d after anthesis and 25-30d after anthesis. The first peak was much higher than that of the second. Sucrose content and sucrose synthase activity peaked at 20 and 15 d after anthesis in Yumai 66 and Yumai 49, respectively. The sucrose content and sucrose synthase activity in Yumai 66 were higher than that in Yumai 49 during grain filling. ADP-glucose pyro-phosphorylase and starch branching enzyme activity in the kernel of Yumai 66 peaked at 20 d after anthesis. While soluble starch synthase activity peaked at 10 and 20 d after