Binary Differential Evolution algorithm was proposed for discrete optimization problem. Firstly, a new operator, boundary-handling operator, was added to the original Differential Evolution to ensure each population generated by the mutation and crossover operator comply with the boundary constraints. Then a new hybrid coding Differential Evolution algorithm with mapping method was put forward to deal with the discrete optimization problem. And lastly, a new selection operator was employed to deal with constraints directly. Two initial simulation results of knapsack problem with different variables show it is effective and useful. Hybrid coding Differential Evolution algorithm is a new effective way for solving the discrete optimization problem.