The invention discloses a seamless riding undergarment with a color-changing and three-dimensional structure, which comprises a hem, a belly part, a waist part, a chest part, shoulder parts, a neckline, armholes, sleeves, cuffs, a back part, a hip part, and underarms. The seamless riding undergarment is characterized in that the belly part and the shoulder parts comprise diamond mesh effect three-dimensional structure areas, the chest part and the hip part comprise narrow cross strip effect three-dimensional structure areas, and the underarms comprise wide cross strip effect three-dimensional structure areas. The seamless riding undergarment is comfortable to wear, and has a color-changing effect and moisture transfer, fast drying and bacteria inhibition functions.