The experiments were carried out in ponds of Shanghai and Gu-angdang province. The gonad development and inducing results of silver carp and bighead were observed annually from age 1+ to 4 on 4 populations, of which two of them were the natural populations from Changjiang and Zhujiang Rivers,the other two populations were from hatcheries of Changjiang and zhujiang river systems. The fish raised in Guangdong matured one year earlier than those raised in Shanghai, it is coincident with the fish from the original rivers.In the same cultivated environment the two natural populations and two hatchery populartions all matured in the same month and were suceessful in induced spawning.The results indicate that the environmental factors play an essential role in gona-dal maturation of silver carp and bighead,while the artificial reproduction does not cause the earlier maturity under non--inbreeding condition. It is estimated that the demand of total heat far maturity of silver carp is about 20,000 degree-days and for bighead is about 26,000 degree-days.