The invention provides a sand prevention device, which comprises an outer pipe, an inner pipe and a sand prevention joint, wherein each of the inner and outer pipes is of a hollow structure, the inner pipe is arranged in the outer pipe, and a first accommodation cavity is formed between the outer wall of the inner pipe and the inner wall of the outer pipe; the sand prevention joint is arranged at the second end of the inner pipe, a first through hole is formed in the sand prevention joint, and penetrates through the upper and lower bottom surfaces of the sand prevention joint, a sucker rod is arranged in the first through hole in a penetrating manner, the first end of the sucker rod is connected with an oil pump, and a second accommodation cavity is formed between the outer wall of the sucker rod and the inner wall of the inner pipe; at least one second through hole for communicating the first and second accommodation cavities is formed in the sidewall of the inner pipe, the bottom end of the second accommodation cavity is communicated with the oil outlet of the oil pump, and the top end of the first accommodation cavity is communicated with a flow string. According to the sand prevention device, the overhauling frequency of the screw oil pump is reduced, and the working efficiency of the screw oil pump is improved.