In order to provide a reference for wind load value of circular cylinder structures in tandem arrangement, time averaged pressure distribution and aerodynamic force of flow around single circular cylinder, two and three circular cylinders in tandem arrangement under different spacing are investigated through pressure-measured rigid model wind tunnel tests. The spacing ratio L/D for two and three circular cylinders in tandem arrangement ranges from 1.2 to 12.0, where D is the diameter of single circular cylinder and L is the distance between the centers of two circular cylinders. The Reynolds number is 3.4×104. Aerodynamic interference effects on time averaged pressure distribution and drag force of three circular cylinders are discussed by comparing to those of single circular cylinder. The variation of interference effect with number of cylinders was studied by comparing with those of two circular cylinders. The research results show that there are two different flow fields for three circular cylinders in tandem arrangement. The critical spacing ratio,(L/D)cr is between 3.5 and 4.0. There exists significant differences between time averaged pressure distribution and drag force under two flow fields.