Volute profile exerts great influences on flow losses and aerodynamic performance of squirrel cage fan. In practical, equilateral- or inequilateral-element method is usually applied to design the volute profile for convenient manufacture. This kind of volute profile consists of several arc segments, however, is discontinuous for curvature radius at the junctions of adjacent arc segments. To overcome this issue, we propose a new volute profiling method to guarantee the continuity of curvature radius along the whole volute profile. By means of three-dimensional computation fluid dynamic simulations, the proposed method is validated through comprehensive comparisons of aerodynamic performances and flow fields of squirrel cage fans with and without continuous curvature radius of volute profile. The results show that the continuous curvature radius of volute profile is of benefit to the aerodynamic performance increase of squirrel cage fan. The velocity downstream the volute tongue is improved. The local sudden diffusion-expansion around the junctions of volute arc segments nearly disappears with continuous increase of static pressure along the volute wall.