The transmitted beam through the large-core multimode fiber is investigated by using CCD beam profiler. The energy distribution and beam quality are discussed, thus the transmission characteristics of the multimode fiber are obtained. The single mode laser is chosen as a testing light source, and the study is conducted by applying multimode fiber with different core diameters and lengths. The results show that the multimode fibers have shaping effect on the input beam including beam quality degradation and homogenization of the energy distribution. Besides, the deterioration of the beam quality and the homogenization effect have dependence on the parameters of the multimode fiber. The larger diameter of the multimode fiber leads to more serious deterioration of the beam quality as well as better homogenization effect. A positive correlation between the transmitting length and the homogenization effect is also found. This study can provide a simple and effective scheme for the shaping of the single mode laser. By selecting multimode fibers with various parameters, the quasi uniform beams with different characteristics can be got to meet special laser processing demand.