The invention discloses a cooling and inner wall lubricating device for a magnesium alloy continuous casting liquid-solid converter. The cooling and inner wall lubricating device comprises an inner wall which is formed by splicing a plurality of layers of curves, and a back plate is matched with the inner wall to form a junction face in which cooling water can be introduced. The inside of the junction face is divided into a plurality of cooling areas from top to bottom, and each cooling area is provided with an independent water inlet and a water outlet. Gaps are reserved between the splicing faces, formed by the curves, on the inner wall, and the gaps communicate with lubricating oil through holes formed in the back plate to provide a lubricating channel between a magnesium alloy coagulating shell and the inner wall. According to the cooling and inner wall lubricating device, cooling and lubricating are both combined into the inner wall and the back plate, the cooling water can be introduced into the junction face to cool the inner wall, and the heat of molten state magnesium alloy in the inner wall is taken away, so that the temperature of a contact part is lowered to be below a solidification level, and a liquid-solid converting effect is achieved. The friction force of a casting blank shell and the inner wall of a coagulator can be lowered, the shell removing effect of casting blanks is improved, and the throwing speed of the casting blanks is improved.