The invention relates to the technical field of the frozen soil cast-in-place pile foundation of a power transmission line, in particular to an inner and outer pile casing construction method for a frozen soil area pile foundation. The inner and outer pile casing construction method for the frozen soil area pile foundation is characterized in that the rotary drilling rig pore forming technology is adopted in a pile foundation pore forming stage for construction; in the digging and pouring process, the inner pile casing and the outer pile casing are cooperated to construct so as to achieve the effects of quick pile foundation pore forming and stable pit wall in the pouring process on the premise of reducing pit wall collapse; the outer pile casing is rolled by increasing 200mm on the basis of the basic diameter, the height is 3m, a reinforcing plate with the width of 200mm is respectively additionally arranged on each of two ends, and four eyeholes of phi 25mm are evenly dug; and the inner pile casing is processed according to the basic diameter, the height of the inner pile casing is determined according to the upper limit value of the frozen soil, and the inner pile casing is generally manufactured into a standard knot of 3m. According to the inner and outer pile casing construction method for the frozen soil area pile foundation, the problem of the warm season construction of the cast-in-place pile foundation of the multi-year frozen soil area is solved, and the disturbance to multi-year frozen soil is reduced, thereby being favorable for the environment protection. The construction quality and the work efficiency of the pile foundation are improved, and the engineering cost is reduced. The inner and outer pile casing construction method has a simple structure, is convenient and quick to use and is economical and practical, and the days for construction are reduced.