Abstract: In response to the natural cleavage in the coal rock body, there are multiple crack initiation and expansion of the engineering perturbation of the mutual influence of the problem, produced 30 prefabricated cleavage width of 0.3mm, respectively, containing 15 °, 30 °, 45 °, 60 °, 75 ° different angles and 20, 30, 40mm different spacing of the parallel double-cleavage sandstone disk specimens, in the RMT-150B rock mechanics testing machine Radial loading test was carried out, and the change rule of strain field on the surface of the specimen during the loading process was analyzed by combining with DIC digital image method. The results show that: The two crack tips of the upper prefabricated cracks near the loading end were the first to crack first, while the two crack tips of the lower prefabricated cracks cracked with a lag; The expansion angle of the crack affects the final crack penetration mode of the specimen, which is mainly manifested as nearly vertical penetration and the penetration mode with a deflection of no more than 45°. When the angle of the prefabricated crack is less than 30° and the spacing of the cracks is less than 20 mm, the expansion direction of the four cracks produced by the prefabricated crack is almost perpendicular to the direction of the prefabricated crack, and as the angle and the spacing increase, the expansion paths of the tips of two cracks of the lower prefabricated cracks are significantly deflected, and the maximum deflection angle can reach 45°. significantly deflected, and the maximum deflection angle can reach 45°; The spacing of prefabricated cracks is more significant relative to the angle of the cracks for the interactions of cracks, when the spacing of prefabricated cracks and the angle of the cracks are small, the interaction between crack initiation and extension is significantly affected, when the spacing of prefabricated cracks is more than 30mm and the angle of prefabricated cracks is more than 30°, the extension of the cracks of prefabricated cracks is almost independent of the influence of each other; The peak load of the specimen is closely related to the damage mode, when the angle of the prefabricated crack is greater than 45°, the specimen shows tensile-shear composite damage with higher peak load, when the angle of the prefabricated crack is less than 30°, the specimen shows tensile damage, and when the specimen tends to be tensile damage, the peak load is lower. The research results have important theoretical significance for the in-depth understanding of the damage mechanism of multi-fractured and multi-cracked coal rock bodies.