In this paper, the nano-sized SO4(2-)/TiO2 solid superacid photocatalysts have been prepared by the method of hydrothermal heating the mixed solution of Ti(S04)2 and urea, heating-decomposing, wet impregnating-calcining. The middle products and the ultimate products have been characterized by XRD, BET, FTIR, DRS and FS. The degradation of rhodamine B by photocatalyst was regarded as a model reaction. The optimum condition of preparing SO4(2-)/TiO2 photocatalysts has been chosen. The results show that hydrothermal treating the solution of Ti(SO4)2 can get the anatase nano-sized TiO2 in the weak alkalinity medium; at 300 degrees C by-products of hydrothermal reaction, such as (NH4)2SO4 and so on, can be decomposed by calcining for 4 hours, avoiding much loss of H2SO4; the most important factors that influence the photocatalystic activities of SO4(2-)/TiO2 are the concentration of SO4(2-) on TiO2 and the calcination time. SO4(2-)/TiO2 photocatalysts have the best photocatalystic activities, up to the level of P-25 photocatalyst, when the concentration of SO4(2-) on TiO2 is 11% and the calcination temperature is 450 degrees C.