The output characteristics and their influence factors of continuous wave (CW) high power Yb3+-doped double clad fiber laser (YDCFL) are experimentally investigated. The results show that the slant angle of the dichroic mirror (DM) with respect to the fiber axes affects the threshold and the output power of the laser. The threshold increases and the output power decreases with the increase of the slant angle, however, such influences may be neglected if the slant angle is smaller than ±2°. The effective gain length of the doped fiber may also influence the threshold and the output power, and determine the lasing wavelength. The lasing wavelength shifts to longer wavelength as the effective gain length of the doped fiber increases.