Abstract: In order to extend the spermatic fast movement time and lifespan for rainbow trout, and improve the fertilization rate in the artificial propagation process, the paper study the impact of the concentration of NaCl on 3, 4 age of rainbow trout spermatic vitality by microscope observed. The results showed that the spermatic fast movement time and lifespan of 4 age rainbow trout were gradually reduced with the concentration of NaCl increasing, but the spermatic fast movement time and lifespan of 3 age rainbow trout present a kind of parabola-shaped distribution, the time have reached the longest in the concentration of NaCl 0.8%, respectively for (25.20±3.04) s, (75.91±9.87) s. In a concentration of below 0.2%, the spermatic fast movement time and lifespan of 4 age rainbow trout were significantly higher than that of 3 age rainbow trout.