The invention discloses a rock-soil blasting method based on tensile stress. Used materials comprise a large-diameter core drilling machine and an explosive. The method comprises the following steps that 1, the large-diameter core drilling machine is used for enabling a core drill bit to drill to a specified depth; 2, the core drill bit is pulled out, and a coring circular ring, namely, a free face, is formed; 3, a rock core is punched, the bottom of the rock core is filled with the explosive, blasting is conducted, the rock core is taken out, and a regular large-diameter empty hole is formed; 4, on the basis of the free face of the formed empty hole, the steps from the first step to the third step are repeatedly conducted on the periphery of the free face, or holes are directly punched on the periphery of the formed empty hole and filled with the explosive for blasting. The tensile stress is formed by tension waves generated by reflecting of blast waves on the free face, and therefore rock soil is destroyed. According to the rock-soil blasting method based on the tensile stress, operation is easy, the safety is good, high-quality large-diameter empty holes can be formed, the number of blast holes can be decreased, explosive unit consumption can be reduced, blasting vibration can be controlled, the rock soil blasting efficiency can be improved, and blasting construction of city underground engineering can be met.