In order to effectively remove the soluble silicate in water,by taking the groundwater with a soluble sili- cate content of 50 ～60mg/L as the research objective,coagulation experiments for the soluble silicate removal by using different compound coagulants were performed.The results show that (1) when the dosage of Ca(OH)₂ is 450mg/L,the removal of soluble silicate and the turbidity reaches 51.16% and 74. 8%,respectively; (2) with the increase of Ca(OH)₂ dosage (more than 450mg/L),the removal of soluble silicate slightly increases while the pH value of the effluent greatly increases,too; (3) FeCl₃ has a poor removal on soluble silicate (less than 12. 55%) but has an advantage in turbidity control; (4) MgO possesses poor efficiency for both soluble silicate re- moval (less than 14. 53%) and turbidity control,and the optimal MgO dosage is 400mg/L; (5) the compound of FeCl₃ and Ca(OH)₂ possesses good performance on both soluble silicate removal and turbidity control,more than 60% of soluble silicate is removed and the effluent turbidity is less than 0. 65NTU; (6) the compound of FeCl₃ and MgO also possesses good performance on both soluble silicate removal and turbidity control,more than 75% of solu- ble silicate is removed; (7) the compound of Ca(OH)₂ and MgO results in a soluble silicate removal up to 73. 76%,which is relatively less than that contributed by Ca(OH)₂ only (81. 41%); and (8) among the three a- bove-mentioned compound approaches,the compound of FeCl₃ and MgO with a Fe³⁺ dosage of 16. 8 mg/L and a MgO dosage of 500mg/L is the best because it results in a soluble silicate removal of 76. 67% and an effluent tur- bidity of 0. 83NTU,and because it helps to obtain effluent with the lowest pH value,which saves the acid added in the later process.