A water circulating microwave exposure system designed by authors was used to investigate the thermal and nonthermal biological effects at different power density (1.0mw/cm~2

3.9mw/cm~2

6.2mw/cm~2

8.3mw/cm~2

10.5mw/cm~2). The results show that: growth of Raji-Cell is inhibited significantly by microwave exposure in 8.3 mw/cm~2 and 10.5mw/cm~2 groups in temperature controlled test(below 37.0鈩?. That is

the growth curve goes down

rate of inhibition and time of generation increase. The degree of inhibition would increase when the medium temperature was not controlled. And

the mechanisms of thermal and monthermal biological effects were discussed in this paper.