Abstract: In this paper, an approach based on Lagrangian Relaxation to schedule batch chemical processes is presented. The scheduling problem is modeled as a compact MILP formulation. The constraints including both discrete and continuous variables are relaxed and the problem is turned into a two-level optimization problem. The high level is the dual of the original problem, and the low level consists of two subproblems ,one for batch-sizing, the other for deciding the time table. Linear programming and dynamic programming methods are used to solve the subproblems. A feasible solution is then constructed based on the solution of the dual problem. Computational results are given to demonstrate the effectiveness of the approach.