The testis development and spermiation process of Aurelia sp. were observed according to experimental ecology and microscopy. Moreover, all data were analyzed by SPSS 13.0 software. The process of testis development was shown in table 1 and the result showed that it needed about 40 days from ephyrae to medusae, which bell diameter and weight of medusae reached 7.50±0.71 cm and 28.70±6.60 g respectively. Meanwhile, the testis began to appear and develop. The testis became mature after 60 days’ rearing, and its bell diameter and weight was 11.77±0.51 cm and 83.54±10.36 g, respectively. Moreover, the width of testis was about 1.05±0.08 mm at that time. The testis began to degenerate after 90 days since the ephyra stage, and almost disappeared at 110 days. The width and length both grew as the bell diameter being larger in the process of testis development. The process of testis maturation of Aurelia sp. was shown in figure 2, which showed the different growth stages of sperm follicles. The maturated male gonads would release sperms once the environment was suitable. The maturated testis released sperm filament containing large amounts of sperms (figure 3A), then the sperm filament (figure 3B) went through gastric circulation groove and gastric-oral arm groove successively, and left the body through oral arm groove finally (figure 3C). Furthermore, the vitality of sperm was also tested and relationship between Aurelia sp. percentage of active sperm and time was shown in figure 4, which indicated that the highest moving time and life span was 4 h 30 min and 10 h respectively (temperature, 22℃; salinity, 30 and pH, 8.0). In conclusion, the testis of Aurelia sp. develops rapidly, the spermiation is simple, and the sperm is of high motility and long life span. Those reproductive strategies are not only laid a solid foundation for Aurelia sp. outbreak but also one of the reasons why this species may be alive for long on the earth.