Abstract: Combining particle swarm optimization algorithm and greedy idea，a Very Greedy Particle Swarm Optimization algorithm（VGPSO） is proposed for Knapsack Problem（KP）.The strategy of dealing the overweight particle is to take out the enclosed and the worst goods in ratio between value and weight，until to satisfy the weight constraint.Simultaneously，the question of sensitive parameter’s choice is avoided under this measure.The strategy of managing the feasible particle is to enclose the goods which is out of knapsack and best in ratio between value and weight，until none goods can be put into.Based on the classic instances in the reference numerical experiments are made and compared with other algorithms.The VGPSO is better than Hybrid Genetic Algorithm（HGA），Greedy Genetic Algorithm（GGA） and Greedy Binary Particle Swarm Optimization Algorithm（GBPSOA） in the ability of finding optimal solution，the efficiency and the robustness.