In order to improve the beam quality of the laser diode and make it meet the requirement of high precision interferometric measurement for large distance, we propose a beam shaping method by using spatial light modulator based on the complex amplitude modulation algorithm. The laser diode beam is shaped to the non-astigmatic fundamental mode Gaussian beam, which has the advantages of good collimation and symmetrical spot shape. Experiment for analyzing the beam quality of the shaped beam is performed, and the results show that the M2 factors in the x and y directions of the shaped beam are close to 1 and the astigmatism of the shaped beam is close to 0, which verify the effectiveness of the proposed beam shaping method. The beam shaping method is applied to large distance interferometric measurement. Displacement measurement with micrometer steps is carried out at a distance of 8 m, and sub-wavelength accuracy is achieved compared with a nanometer stage. Experimental results indicate that the shaped beam can meet the requirement of large distance interferometric measurement, which verify the feasibility of the proposed beam shaping method.