Poly(oxypropylene-oxyethylene glycol) block copolymer(PBC) oil dispersant, which has low toxicity, high biodegradability, and an excellent dispersion efficiency to crude oils and weathered W/O emulsion was prepared by blending PBC, poly(oxyethylene) oleate, and sorbitan monooleate. The dispersing efficiency was measured by swirling flask method. The PBC oil dispersant had an excellent dispersing efficiency to weathered oil products formed as stable W/O emulsion, and the low toxicity, such as 4000 ppm to Oryzias Latipes(24 hr, TLM), Brine Shrimp Artemia(24 hr, TLM).