Abstract: Taking the coal seam roof sandstone in the Hexingliang mine field in the Yushen mining area in northern Shaanxi as the research object, the uniaxial compressive strength test is used to test the rock with a diameter of 50mm, an aspect ratio of 0.5 and a diameter of 70mm and an aspect ratio of 0.7. The uniaxial compression was carried out, and the effects of the post-peak failure modes of two intact rock specimens with different aspect ratios and the end restraint effect on the test results of two different aspect ratio specimens in the uniaxial compressive strength test were analyzed. It was verified that the uniaxial compressive strength of a non-standard morphological rock sample with a diameter of 70 mm and an aspect ratio of 0.7 was converted into a uniaxial compressive strength of a standard morphological rock sample with a diameter of 50 mm and an aspect ratio of 0.5. Applicability of the experience conversion formula. The test results show that under the condition of uniaxial compression, the fracture morphology of the complete specimen with 0.7-diameter height ratio is dominated by fracturing failure, while the failure mode of the complete specimen with 0.5-diameter height ratio is dominated by shear failure; At the same time, the calculated value of the 0.7-axis height ratio rock sample through the uniaxial compressive strength empirical conversion formula is greater than 0.5 diameter-height ratio in a certain range, and the measured uniaxial compressive strength value of the standard morphological rock sample; for fine sandstone, the diameter is high. When the uniaxial compressive strength value of the non-standard morphological rock sample with a ratio of 0.7 is converted to the standard uniaxial compressive strength value with an aspect ratio of 0.5, the above formula has good reliability, comparability and applicability.