The slip rate of rubbertired tractor is high and the adhension is low when smallwheeled tractor working in dryland, which affects exerting power. Based on the structure parameter of smallwheeled tractor and soil conditions, the parameter equations of the vanewheel were set up,such as external diameter, the number of wheelvane and curvilinear equation.Therefore， the principal parameters of vanewheel for Taishan12 tractor were determined. Compared with the functions of rubber tire working in fields, when a tractor works in raw land and ploughed land, the maxmum drawing power of vanewheel increases by 25.3 % and 15.3 % respectively, and the maxmum drawing force increases by 37.5 % and 24 % respectively.Compared with the 120°angle of vane,the maxmum drawing force of the 150°angle of vane increases by 24 %.