Polysilicate titanium salt (PST) is synthesized by using spent titanium solutions and polysilicic acid (PSiA) as raw materials. PSiA could improve the aggregation ability of titanium salt flocculants and also restrain the hydrolysis of Ti4+ to stabilize titanium salts. Meanwhile, replacing titanium salt with spent titanium solutions could reduce the cost of PST and solve the problem of wastewater treatment in the titanium industry, which makes valuable waste regeneration possible. SEM results show the morphology transformation (sheet, spheroid, and sphere) of PST with different Ti/Si molar ratios. The formation process of PST is analyzed by FT-IR and XPS. This study investigates the effect of Ti/Si molar ratios on PST flocculation performance in humic–kaolin water and actual domestic wastewater treatment. The in situ floc size change of PST is measured by laser particle size analyzer in humic–kaolin water treatment. Additionally, the performance of PST is comprehensively evaluated on flocculation and sedimentation ability, rapid sweep netting ability and stability. In short, the prepared PST in this study is suitable for treating wastewater with high turbidity and COD in a wide range of pH values.