The purpose of development is to provide advanced safety seatbelt restraint system positioning device for different body sizes; it can equip more than one positioning device to lateral sides of seats backrest, or interior plastic kit. The positioning device (1) includes a base (12) and a positioning block (11) fixed to a lateral side of the backrest (31), the positioning block (11) oriented in the same direction as the base (12), a top end of the positioning block (11) is integrally assembled to the base (12), a bottom end of the positioning block (11) and the base (12) are integrally formed as a slot (13) for passing through a seatbelt (41); the seatbelt (41) led into the slot (13) is buckled by the positioning block (11).