Three-year daily field observations show that the number of hours of usual light intensity varies, depending on the sky state for the research area,with the increased(decreased)number on a clear(rainy)day aidlow temperattire in connection with short period of insolation.For the study region,the period of light intensity E> 50lx and the number of insolation > 13h and 45 min spai1s June to August 1,a condition that meets the needs of light for the photoperiod-sensitive genic male sterile rice.