The knapsack problem is an important problem in operations research. By taking some practical instances with the use of the dynamic programming method and integer programming method to solve the knapsack problem, this paper makes a comprehensive comparison of the two methods, and the conclusion is: When the integer programming method is applied to solve the knapsack problem, it is necessary to decide to use implicit enumeration method or branch and bound method according to the type of the knapsack problem. While the dynamic programming method pays more attention to the middle process of putting items.