Typhoon is meso-α scale system and sometimes comparable to large scale system.The isolation of typhoon from the environment flow is an important step in order to investigate the interaction between the environment flow and typhoon circulation.Three methods including time filter,space filter and dynamic method are applied to separate the typhoon Megi (1013) of year 2010 from the environmental flow.The separation results show that,time filter and space filter methods have relative randomness and are somewhat subject to the life cycle and the size of typhoon,which will leave residual typhoon wind to the environmental field,thus weaken the environmental flow;while the dynamic method can well separate the typhoon from the environmental flow.Both advantages and disadvantages exist in the three methods.The time filtered wind field is well balanced with other time filtered fields such as temperature and height.While when using space filter,wind may not be consistent with height due to the different scale between wind,height and temperature field.Nevertheless space filter is relatively simple to use and only need one time series,while time filter needs longer time series,which result in no application of time filter in operational forecasting.Dynamic method is better in performance,but relatively complex and sometimes prone to imbalance in lower level and has much space to improve.