Growth rate, first reproductive age, life span and total offspring numbers were measured to study the effects of water temperature and salinity on the propagation of rotifer, Brachionus plicatilis. Three types of rotifer, Large (L), Small (S) and Thailand Small (TS)-types, were cultured in the $4 imes4$ factorial culture conditions with four different salinities (5, 15, 25 and $35\%o$) at each of four different water temperatures (15, 20, 25 and $29^{circ}C$). The results are as follows; Under the 4 different salinity gradients %$(5\%o,;15\%o,;25\%o,;and;35\%o);at;29^{circ}C$, the mean growth rates of L, Sand TS-type were 0.60, 0.84 and 0.96, respectively. The first reproductive age of three types rotifer appeared to be early at high water temperature. The total offspring numbers of the three types were higher at $25^{circ}C;and;29^{circ}C$, with the maximum value of 28.3 on the average at $29^{circ}C$ for TS-type, and the minimum value at $15^{circ}C$ for S-type. Life span decreased with high water temperature and increased with low water temperature. L-type and TS-type rotifer showed the longest life span of 13.5 days on the average at $15^{circ}C$, and S-type showed shortest 6.2 days on the average at $29^{circ}C$.