The invention discloses a vehicle mechanism capable of adjusting the sitting posture for a massage chair. The vehicle mechanism comprises a massage chair body, a first adjusting mechanism and a second adjusting mechanism; the first adjusting mechanism comprises a first push rod, a second push rod and two limiting blocks, protection soft cushions are arranged on the surfaces of the limiting blocks, connecting bases are installed on the outer sides of the two limiting blocks respectively, the two connecting bases are connected with the first pushing rod and the second pushing rod respectively, a movable plate is arranged on the bottom surface of each limiting block, the massage chair body comprises a cushion part and a backrest part which are connected together through a hinged base, the limiting blocks slide on the surface of a smooth plate freely through the movable plates, and the second adjusting mechanism comprises a first adjusting rod, a second adjusting rod and a third adjusting rod. According to the device, by means of the mode that adjustment in the horizontal direction is matched with adjustment in the vertical direction, the sitting posture is well adjusted, the massage chair is more comfortable, and the vehicle mechanism is worthy of popularization.