Abstract: The effect of alkaline phosphatase (ALP) on calcium metabolism of duck embryo was studied in present experiment The activity of ALP in the bone and plasma and the specific activity in the bone of embryos was tested at the incubated day of 14th, 16th, 18th, 20th, 22nd, 24th, 26th, 28th in the surrogate eggshell cultured group (treatment) and normal one (control). The result showed that the activity of ALP increased significantly from the day of 14th to the day of 28th (P<0.01) both in treatment and in control, but the activity was significantly higher in the former than the latter with the same cultured time (P<0.01). The specific activity in the bone of embryos was higher in treatment than in control after 22nd, like the variation of ALP activity. The result indicated that activity of ALP in the bone and plasma could elucidate the calcium metabolism of the embryos and showed that calcium deficiency was appeared in the later development period of embryo in the surrogate eggshell group.