Abstract: To solve the difficulty of measuring curved body size of pigs and restoring the real body size of pigs with calibrated ruler, landrace was taken as the research object, based on the top and side view depth images of pigs, this paper proposed a method for curved body size measurement of pigs without calibrated ruler. The method used convex envelope and maximum external contour to extract the body measurement points of head, tail, shoulder, hip, and body height, and then measured the body size parameters（body length, shoulder width, hip width, and body height） of the pig. The results showed that in the normal bending range（0°-40°）, the measurement accuracy of shoulder width was the best,with less than 1.92% the average relative error, and the average relative error of hip width, body height and body length was less than 2.00%, 2.64% and 2.93%, respectively; in the non-bending state, the average relative error of shoulder width, hip width, body height and body length was 1.29%, 1.26%,1.92% and 2.33%, respectively, which was better than that of the existing methods. In conclusion, the method proposed in this paper can achieve the measurement of body size in the natural state of pigs with high accuracy, good universality and robustness, which can meet the needs of monitoring the actual growth condition of pigs.