To solve the common problem of casing pipe breaking in DTH hammer drilling with casing and to increase the depth of drilling with casing, double shock of DTH hammer drilling with casing was adopted and casing pipe jar was designed to put external force to the top of the casing in the drilling process. By calculating the force of the jar and analyzing the factors on the maximum drilling depth of drilling with casing, this paper verifies that the impact generated by the jar can drive the casing follow-down smoothly, so as to solve the problem of casing pipe breaking and low depth of casing with drilling.