The specified size of the sample is 100 mm in width, 100 mm in length. According to the direction of warp and weft, take two pieces for a group to prepare two groups in total. The surfaces of the two specimens are overlapped with each other. At 10 mm from one side, a test piece with a seam interval of 20 ± 2 stitches / 100 mm is sewn with a sewing machine, and then installed on the fixtures on the left and right of the testing machine for 2500 times. The load is 29.4N (3kg), and the speed is 30 reciprocating/min repeated reciprocating test. After the test, the size of the small holes in the seam of the test piece due to slippage and other reasons was measured under load, and the fatigue strength of the seam was evaluated and judged.