The invention provides a downpipe frost crack prevention device and is used for solving the problem that an existing building downpipe is prone to bursting by freezing in winner. A solar cell panel is arranged on the upper portion of a support, and an angular adjustment assembly is arranged between the solar cell panel and the support; a solar water heater is arranged on the upper portion of the support, a water storage tank of the solar water heater is connected with a shell body through a water supply pipe, a piston is arranged in an inner cavity of the shell body in a moving mode, an air cylinder is arranged between the piston and the support, a first check valve and a second check valve are arranged at a blocking end of the shell body, and the first check valve is connected with a first water pipe; the second check valve is connected with the water supply pipe, the other end of the first water pipe is connected with a radiator, the radiator is arranged in the downpipe and is in contact with the inner wall of the downpipe in a matched mode, the other connecting opening of the radiator is connected with a second water pipe, and the other end of the second water pipe is connected with the water storage tank. Thawing of freezing formed in the inner wall of the downpipe can be achieved, and the downpipe is prevented from being damaged and busted by freezing.