Maintaining excellent beam quality is very important for the construction of the experimental spectral beam combining(SBC) system. The influence of pointing deviation on the beam characteristic was studied in SBC of fiber laser array theoretically. The incident light field of the laser array with the pointing deviation was corrected, and the variation rule of the combined beam quality with uniformly distributed random perturbations was discussed by the beam propagation model and the statistical analysis. The simulation result shows that the pointing deviation has a significant effect on the output characteristics of the SBC system. When the maximum deflection angle of the laser array is only 0.05°, the beam quality of SBC system will increase to(6.49±1.73). In order to achieve the brightness scaling of combined beam and gradually expand the scale of laser array, the combined beam quality tends to stabilize. As a reference for the array scale(30 fiber lasers) with the changes of relative stability, the variation tendency of the M2 factor and maximum pointing deflection angle is fitted for building the experimental system of SBC.