The observations and histological studies on the gonad index of abalone were carriedout. The results are as follows: 1. The peak of gonad index by weight can not correspond with the period of thematuration observed by histology. 2.The development of the spermaries can be divided into five periods: 1) restingperiod, in early October to January of next year; 2) recovery period. in early Februa-ry to May 3) pre-mature period, in June;4) mature period, in early July to earlyAugust; 5) spill sperm period, in lato August to Septembor. 3. The development of ovaries can be also divided into five pcriods: 1) restingperiod, in early October to January of next year; 2) recovery period, in early Februa-ry to April; 3) growth period, in early of May to the middle of July; 4) matureperiod, in the late of July to early of August; 5) spawning period, in the late of Au-gust to September. 4. If ever the ovaries develop into maturation, the biggest oocyte is only 162μ indiameter, most of them are about 110μ and the mature eggs in shape can be hardlyobsarved. 5. The sex of abalone is usually constant. But an individual of hermaphrodite isobserved.