At present, the research on the scheme of reducing drag around a circular cylinder has always been a hot topic. But there are few studies on the effect of prisms as pin fins on the drag reduction efficiency of cylinder. Based on the Navier-Stokes equations of incompressible viscous flow, numerical simulation of flow past a circular cylinder attached prisms was investigated by using OpenFOAM. A circular cylinder with double prisms placed upstream or downstream, the effects on lift coefficient, drag coefficient and Strouhal number of prisms with different angles and relative gap from the wall have been investigated at Re=200. The numerical results show that the attached prisms can effectively improve the pressure distribution on the cylinder surface and reduce the pressure drag. The drag reduction efficiency of the upstream prisms for cylinder can reach 37.21%, which is higher than that of the downstream prisms. When the prisms are set in the downstream of the cylinder, the restraining efficiency of the cylinder lift is higher than that in the upstream, which can reach 99.86%. When the prisms are placed upstream and downstream simultaneously of the cylinder, the restraining effect on the lift and drag of the cylinder can be further improved. Compared with single cylinder, the average drag coefficient can be reduced by 54.63%, and the lift coefficient can be reduced by 99.94%.