The sperm motilities were determined by using phase contrast microscope and analytical system of computer. The result s show the sperm activity rate signif icant ly increases( P < 0. 01) w ith the concentration of NaCl when that of NaCl ranges from 0 to 0. 3% in Monopterus albus, but the sperm activity rate, linear velocity of the spermatozoal mot ion and the frequency of flagellar beat of spermatozoa signif icantly reduce ( P < 0. 05) when the concentration of NaCl exceeds 0. 7% . The micropylar region of the mature egg is like a funnel cave in M. albus under scanning electron microscopy. A micropylar canal is located at the central section of the bottom of the cave, about 4. 22 .. 0. 66 ..m in diameter. The penetration of sperm into the eggs is slow and the process of the fertilization is long. The sperm originally arrives at the surface of the chorion of M. albus 30s after insemination. The micropylar canal is blocked by the fertilized plug within 5 minutes after insemination.