The present invention provides use of a photoperiod-sensitive genic male sterility mutant of cotton in crossbreeding or hybrid seed production. The fertility of the photoperiod-sensitive genic male sterility mutant of cotton is influenced by the photoperiod. The photoperiod characteristic of the photoperiod-sensitive genic male sterility mutant of cotton is that, the photoperiod-sensitive genic male sterility mutant of cotton shows normal fertility when the illumination time is shorter than 11.5 h and shows genic male sterility when the illumination time is longer than 12 h; the photoperiod-sensitive genic male sterility mutant of cotton is in a fertility change period when the illumination time is in a range of 11.5-12 h and has less pollen. The photoperiod-sensitive genic male sterility mutant of cotton is PSM1, and/or a photoperiod-sensitive genic sterile line obtained through selective breeding of hybridized and/or backcrossed and/or self-bred offsprings of the PSM1.