The chest pad of seamless underwear is not fixed, which is convenient to carry and use. According to relevant public information, the patent technology of the present invention provides a seamless underwear and a processing method thereof. Soft feel, high elasticity, good flexibility, strong resilience after stretching, and not easy to wrinkle. There is no sewing thread, and super-large stretching does not hurt the body. The chest pad is fixed in place and durable, and the lower circumference does not relax and deform after repeated washing.