To solve the problem of high cost for traditional method of hybrid seed production which involves hand emasculation followed by pollination, a largescale cotton tissue culture was carried out to creat a cotton mutant and developed a highly sensitive genetic male sterility since 2006. In 2012, a photoperiod sensitive genetic male sterility was screened out in their offspring which named PSM4 (Photoperiod sensitive genetic male sterility mutant of cotton). During 2012-2017, breeding,material selection, the growth and development investigation and characteristics of photoperiod were carry out in the experimental field of CRI (Cotton Research Institution of China) in Anyang, Henan Province and South Crop Breeding Base in Zhongliao Village, Jiyang Town, Sanya, Hainan Province. （1） PSM4 shows male sterility when the sunshine duration is more than 12 h; when between 11.5-12 h, it is in the fertility transformation stage; when less than 11.5 h, it shows normal fertility. （2） Shading experiments show that the crucialtime of anther and pollen abortion at 12-15 days before anthesis.（3） Paraffin section of anther shows the reason of pollen abortion is the lost of extine under long daylight exposure. （4） All individuals were fertile in F₁ population from the reciprocal crosses between PSM4 and six upland lines and the results shows that the photoperiod sensitive genetic male sterility character is controlled by their nuclear genes. Genetic studies indicate that PSM4 fertility was controlled by single recessive genes for the segregation of fertile and sterile plants ratio of 3∶1 in F₂ population and unaffected by the rainy weather. The successful cultivation of PSM4 will greatly advance the study of hybrid seed production and use in an industry revolution in cotton breeding.