Abstract: Based on Fresnel-Kirchhoff diffraction integral theory, output beam properties of fiber-coupled LD array and their impacts on oscillating light are examined. The results show that deviating from Gaussian distribution, the output light intensity on the exit surface of the optical fiber is in multi-peak distribution. Positions of peaks are sensitive to LD beam directions, and will change with the variation of LD beam directional angle and spatial location. This phenomenon is a result of various factors. Pump light with multi-peak distribution has a direct impact on the mode structure of the oscillating light. The more pump light intensity peaks concentrate in center, and the more convex of the light intensity is, the better oscillating light beam quality will be, which should be considered in laser-diode pumped solid-state lasers design.