Experiments were conducted to examine the effects of salinity fluctuation frequency on the osmolarity, Na+-K+-ATPase activity and HSP70 of Chinese shrimp Fenneropenaeus chinensis with initial wet body weight of 1.460g±0.091 g. The salinity in the control group (DO) was 28 throughout the experiment, whereas treatments D2, 134, 196 and D8 were subjected to different salinity fluctuation frequencies of 2, 4, 6 and 8 d, respectively. The salinity in treatments D2, I34, D6 and D8 was kept at 28 for 2, 4, 6 and 8d, respectively, decreased abruptly to salinity 24, lasted for another 2d, and then was raised to its initial value 28. This was a complete salinity fluctuation cycle that afterwards repeated itself. After 32 days, the osmolanty in treatments D2, D4, D6 and D8 was signifi-cantly lower than that in treatment DO (P