The objective of this paper is to extend existing concurrent tolerancing model and develop an integrated optimization approach that can simultaneously carry out concurrent tolerance allocation and complete the selection of machining methods. The proposed modeling approach takes the minimization of total production cost including manufacturing cost and quality loss as the objective function, and takes the product function requirements, the economic machining tolerance range for each alternative process operation, and machining method selection as the constraints, the MATLAB R2016b is employed as a nonlinear programming technique to solve the optimization model. The numerical example of a gear assembly is given to validate the proposed approach.