Based on the optical refraction characteristics of transparent solid medium, the error analysis of the traditional method for measuring the refractive index of transparent solid using laser speckle is carried out, and an improved method to reduce the error is proposed. Firstly, an image speckle measurement system has been set up with the transparent solid placed between the imaging lens and CCD. After that, the two speckle patterns are collected by the CCD when the transparent solid is placed perpendicular to the optical axis and deflecting to a certain angle respectively. A speckle in-plane displacement can be obtained by processing the above two speckle patterns using the digital image correlation method. Finally, the refractive index of solid can be calculated based on the theoretical formula. According to the comparison experiments, the measurement results show that this improved method has smaller error and higher precision.