Abstract: Two hundred healthy lancelets, measured their length and weight, were divided randomly into two groups (100 lancelets per group) and cultured respectively in the nature seawater (marked as NS group) and the artificial seawater (marked as AS group). The livability, length, weight and the gonad diameter of the lancelets reared in these two culture systems were measured respectively. The results were as follows: the average length value of the NS group was markedly higher than that of the AS group. But there were no markedly differences in the livability, the average weight and the average gonad diameter values between the tow groups. The gonad development of the NS group was synchronous with that of the AS group. In addition, their spawning was observed during the generation season.