We investigated the optimum salinity and temperature conditions for mass culture of ultra-small rotifer Synchaeta kitina. In the salinity experiment of ranging within 5 and 30 psu, the population growth of S. kitina increased continuously up to 20 psu, and then decreased over 20 psu. Their maximum density showed 390.1 inds./mL at 5 psu. A pre-reproductive phase was shortened in low salinity than high salinity. Also, the maximum offsprings and maximum lifespan and lifespan of the female were 13.4 inds. and 5.9 days, respctively at 5 psu. In the temperature experiments of ranging within 16 and $32^{circ}C$, the population growth of S. kitina increased continuously up to $24^{circ}C$, and then decreased over $24^{circ}C$. The highest maximum density showed 492.8 inds./mL at $16^{circ}C$. Their offsprings increased significantly with temperature decrease, and the maximum number of offsprings per female was 9.2 females. at $16^{circ}C$. Their lifespan increased with temperatures decrease and the longest lifespan was to 5.5 days at $16^{circ}C$. From these results, we conclude that the optimum culture conditions of S. kitina is 5 psu and $16^{circ}C$.