Abstract: This experiment was conducted to study the biochemical characters and effects of surface polymers from the nematode-trapping fungi, Arthrobotrys oligospora. The surface polymers were extracted by optimized method with 5 mol·L-1 LiCl, then proteins concentration, enzyme activity and toxicity of the surface polymers to nematodes in vitro were determined. Meanwhile, the effects of temperature, pH, chemical reagents and protease inhibitors on the surface polymers were also studied. The result showed that the protein contents and protease activity of the surface polymers from mycelium with traps was significantly higher than that from general nutrition mycelium and protease, acid phosphatase and alkaline phosphatase were detected for the first time. The optimal temperature was 65 ℃ for both polymers. The optimal pH were 7.0 and 6.5-7.5, respectively. They both had low toxity to nematodes tested. All above results indirectly confirmed the effects of surface polymers on the preying process, and a preliminary understanding of composition and biochemical characters of the surface polymers were carried out. It also provided valuable information for the studies on the mechanism of nematode-trapping fungi in future.