Reconfigurable intelligent surface (RIS) is a popular technology for 6G. The joint optimization model of RIS location and parameter for RIS aided multi-user broadcast channel is proposed. With highly nonlinear objective function and discrete phase constraints, it is formulated as a mixed integer programming problem. The Courant penalty function technique from optimization and the maximum ratio transmission technique from communication are applied for problem simplification. Then the RIS parameters are updated in closed form, and its location variables are solved through the trust region method. Numerical tests show solid improvement of the quality of service by the new model compared to the work which only optimizes RIS parameters. The advice of RIS location is also provided.