The unstability of cytoplasmic male sterilities (CMS) of Brassica napus Lwas stud-ied from 1989 to 1992,and the results indicated: 1. The occurrence of trace-pollen plants In sterilematerials was caused by nuclear polygenes of the maintainers; 2. Progenies of partial sterility typeshowed segregation of sterile, partially sterile (with trace pollen )and fertile plants; 3. High andlow temperature CMS lines were crossed and its progenies manifested complex segregation; 4.There was a tendency to increase the fertility with successive selfing of the high temperatureCMS line. The unstability of cytoplasmic male sterilities (CMS) of Brassica napus Lwas stud-ied from 1989 to 1992, and the results indicated: 1. The occurrence of trace-pollen plants In sterilematerials was caused by nuclear polygenes of the maintainers; 2. Progenies of partial sterility type showed segregation of sterile, partially sterile (with trace pollen) and fertile plants; 3. High andlow temperature CMS lines were crossed and its progenies manifested complex segregation; 4.There was a tendency to increase the fertility with successive selfing of the high temperatureCMS line.