Abstract: A pilot gust generator is as experiment object,by measuring the flow field of the gust generator in different situations with two dimension hot wire anemometer,the measurement scheme and online measuring angle correction,and the calculation of the gust amplitude and flow fluctuation are proposed.Experiment results show that online angle correction used can improve the accuracy and efficiency of two dimension hot wire in Y direction,phase analysis used can sat-isfy the calculate the amplitude and fluctuation of periodic gust.Gust amplitude is in direct ratio with the vane oscillation frequency of 4 ~ 15Hz,oscillation angle of 8°~ 30°,and vane chord length of 50~100mm.Unstability (velocity fluctuation at same phase)of the gust flow has a cer-tain linear relationship with the vane oscillation angle and wind speed,which increases while the vane oscillation angle and wind speed increase in the test range,at the same time,proper vane os-cillation frequency can decrease unstability.The conclusion is helpful for the gust generator de-velopment and flow field measurement in wind tunnel.