The invention relates to the technical field of surveying instruments, in particular to a portable surveying instrument supporting device and a using method thereof. The portable surveying instrument supporting device comprises a supporting box, first supporting plates are hinged to the left side and the right side of the top end of the supporting box, first sliding grooves are formed in the two first supporting plates, first sliding blocks are slidably arranged in the two first sliding grooves, the ends, close to the center face of the supporting box, of the two first sliding blocks can be fixedly connected with first connecting plates, the ends, away from the two first sliding blocks, of the two first connecting plates extend to the outer sides of the two first supporting plates correspondingly and are fixedly connected with second supporting plates, the ends, close to the center of the box body, of the two second supporting plates make contact, a first fixing groove is formed in the right end of the second supporting plate located on the left side, and a second fixing groove is formed in the position, corresponding to the first fixing groove, of the left end of the second supporting plate located on the right side. The portable surveying instrument supporting device is convenient to fold, the occupied space area during carrying is reduced, the portable surveying instrument supporting device is convenient to carry, and the use convenience of the portable surveying instrument supporting device is improved.