With the gantry angles of 0°-80° and 280°-360°(0°), the off axis distance (OAR) profiles curves of 6 MV X-ray were obtained by Monte Carlo simulation, 3-D water phantom measurement and MatriXX measurement. Comparing the three types of curves, we analyzed the angular dependence of MatriXX 2-D chamber array. The results revealed that the three types of curves agreed well with the gantry angles of 0°-60° and 300°-360°(0°). Curves and centre point dose on plane from Monte Carlo simulation differed obviously from those of MatriXX measurement in gantry angles of 70°-90° and 270°-290°. It is possible to verify the dose distribution of intensity modulated radiation therapy (IMRT) plan using the Multi-Gantry-Angle Composite (MGAC).