Abstract: A laboratory experiment was conducted to study the effects of different population density (D₁: 100 ind·L^-1, D₂: 150 ind· L^-1, D₃: 300 ind·L^-1) and culture volume (V₁: 50 mL, V₂: 100 mL, V₃: 400 mL) on the growth and reproduction of Moina irrasa at 25 ℃. At the same culture density, the body length of the M. irrasa females at their first pregnancy, the first brood, and the total offsprings per female decreased with the increase of culture volumes, while the sex ratio (male/female) of the offsprings was in adverse. At the same culture volumes, the total offsprings per female decreased with the increase of culture density. At D₁V₁, the body length of the females at their first pregnancy (095±010 mm) and the total offsprings (171.3±19.8 ind) per female were the maximum.  At D₃V₂, the sex ratio was the maximum (0.54±0.05). Culture density, culture volume, and their interactions significantly affected the total offsprings per female and the sex ratio (P<0.001).