The activities of ACP and ALP in hepatopancreas and gonads of immature, precocious and normally mature Eriocheir sinensis were assayed at 520nm wave length. Firstly, the activities of ACP and ALP in hepatopancreas were significantly higher than those in gonads. Secondly, the activities of ACP in hepatopancreas of precocious crabs were significantly higher than those of immature crabs, but lower than those of normally mature crabs, and no sexual difference existed. However, the activities of ACP in ovaries of precocious and normally mature female crabs were correspondingly lower than those in testes of precocious and normally mature male crabs. There was no difference between precocious and normally mature crabs. Thirdly, the activities of ALP in hepatopancreas of precocious female crabs were significantly higher than those of immature and normally mature female crabs, but at the same level as three groups of male crabs. However, there was no significantly difference between the activities of ALP in gonads of precocious and normally mature crabs. Therefore, the following could be concluded： （1）mobilization or synthesis of those nutrients required by gonads was related to ACP in hepatopancreas; （2）onset of precocity was related to significant elevation of activities of ACP and ALP.