To study the mean aerodynamic characteristics of two square cylinders arrangement inline at different incidence angles and spacing ratios， the wind pressure from a wind tunnel test on a rigid model is adopted. The mean lift and drag coefficients of two square cylinders at 0°≤α≤90° and 1.2≤L/D≤8 are measured and analyzed. The results show that the mean aerodynamic characteristics of the two square cylinders are divided into three types according to the incidence angles， which are the small incidence angles （0°≤α≤10°）， the moderate incidence angles （10°＜α＜60°）， and the large incidence angles （60°≤α≤90°）. At small incidence angles， the mean aerodynamic coefficient obviously jumps at critical spacing ratio ranging from 3 to 4. At moderate incidence angles， with the increase of spacing ratio， the mean drag coefficient of upstream square cylinder decreases at first and then increases， and the mean lift coefficient changes little； the mean drag coefficient of downstream square cylinder gradually increases， and the mean lift coefficient gradually decreases. At large incidence angles， when L/D≤2， with the increase of spacing ratio， the mean drag coefficient of upstream square cylinder gradually decreases， and the mean lift coefficient of upstream square cylinder decreases at first and then increases； the mean drag coefficient of downstream square cylinder decreases at first and then increases， while the mean lift coefficient is in opposite direction. In addition， when L/D≥2.5， the mean aerodynamic coefficient of the two cylinders slowly changes with the increase of the spacing ratio.