Child vehicle seat

A child vehicle seat comprises a supporting part, wherein the supporting part is provided with a base part put on a pad of the seat and a backrest put close to a backrest of the seat; a coupling and a tensioning device controlled by a control lever that are used for coupling to and tensioning a seat security belt of the vehicle are set in the base part; the coupling and tensioning device comprise a translating body; the translating body is provided with a wedge end that is suitable for sliding in a wedge-shaped cavity set between two oppositely-sliding parts of the base part; the parts are capable of penetrating through the wedge-shaped cavity on the wedge end of the translating body and the parts are moved parallel and vertical to the translating body; part of the vehicle security belt is placed between the cavity and the end portion and the part is also related to a slide portion of the base part; and by inserting the end portion into the cavity and the movement away from each other caused by inserting the part, the security belt is tensioned. The arrangement has simple configuration and small amount of components, thus compared with the existing technology, greater reliability is provided and the cost is reduced.