For testing the wavefront error of large aperture telescope in the outfield, a Shack-Hartmann wavefront sensor with high detect ability was developed. Using star as light source, the wavefront error of the telescope with 1 m diameter and 11 m focal length was test through the sensor. The results show that the wavefront error of the telescope is about 0.39λ~ 0.46λRMS, and the error increases as the elevation angle of the telescope. The dominating aberration is 3rd 0°astigmatism, and the result is identical to that of star test.