This paper mainly discusses the influence of sodium alginate to polyester fabric in the process of wool-like. Polyester is pre-treated by sodium alginate solution firstly, and then modified by caustic soda, at last, the sample is steamed in the saturated vapor. Wool-like effect changes along with the concentration of sodium alginate and caustic soda, steaming time are analyzed. The results show that wettability, warmth retention and fullness of wool-like fabric are improved obviously. So treated with sodium alginate and then caustic soda can give polyester fabric ideal wool-like effect.