Abstract:For securing the ones network it is important to detect botnet. For improve the efficiency and accuracy in data mining use optimization techniques. One of the current application areas is outlier detection that has not been fully explored yet but has enormous potential. Web bots are type of outliers, They can be found in the web usage analysis process.Particle Swarm Optimization (PSO) based on Hierarchical method is used in this paper to detect web bots among genuine user requests. In proposed scenario deal with tuning parameters in PSO algorithm for selecting the process. It is necessary to set different strategies for each PSO parameter. These parameter selections should ne optimum. HPSO algorithm provides high accuracy, fast convergence results. Less computational time to execute this process is the main advantage.