Abstract: Soft coal of 66207 working face in Xinzhuangzi Coal Mine in Huainan Mining Area was taken as the research object in order to obtain the effect of different ratios of thickness to radial dimension and moisture content on soft coal splitting strength. Brazilian splitting test of coal with different ratios of thickness to radial dimension and moisture content were carried out, and the results were taken into the tensile formula considering filler strip and sample contact angle. The results showed that when moisture content is similar, with the increase of ratio of thickness to radial dimension of sample, tensile strength decreases gradully, the downward trend of ratio of thickness to radial demension and tensile strength curves slow down, and the curve is approximately level after the ratio of thickness to radial dimension is greater than 0.6; when the ratio of thickness to radial dimension is the same, with the increase of moisture content, tensile strength of coal sample is on the decline as a whole.