In this paper, the effect of sodium alginate on the flotation separation of scheelite from calcite and fluorite using sodium oleate as collector was investigated. Flotation results showed that sodium alginate could selectively depress the flotation of calcite and fluorite in pH range of 7-12 when it was added before sodium oleate. The selective depressant effect of sodium alginate was studied using zeta potential measurements, contact angle measurements and FTIR. The zeta potential measurements results showed that sodium alginate exhibited little influence on the surface charge of scheelite but had remarkable effect on that of calcite and fluorite. The results of contact angle measurements indicated that sodium alginate could produce selective, non-recoverable decrease in surface hydrophobicity of calcite and fluorite. The FTIR studies demonstrated the chemical absorption of sodium alginate on calcite and fluorite surface and no form of adsorption on scheelite surface.