In order to study the frequency domain characteristics of wind loads on high-rise buildings under downburst，using the impinging jet device to simulate thunderstorm downburst，pressure test was carried out on rectangular high-rise building models with different aspect ratios（D/B）. According to the test data，the power spectrum densities，correlation coefficients and coherence were analyzed in detail. The results show that the drag coefficient spectra are consistent with those of longitudinal wind spectrum of oncoming wind. With the increase of radial distance，the bandwidth of the drag coefficient spectrum becomes wider，and the main frequency and energy gradually decrease. The lift and torque coefficient spectra vary with the increase of the aspect ratio of the models，but the change is not obvious，which may be mainly affected by the special turbulent wind field of thunderstorm downburst. The radial distance and the aspect ratio have greater influence on the correlation of the drag coefficient，but less on the correlation of the lift and torque coefficients. The coherence of layer drag coefficient decreases linearly with the increase of frequency. The coherence of layer lift coefficient keeps stable in low frequency band，and it decreases exponentially with the increase of frequency. The layer torque coefficient is relatively small，and it decreases exponentially with the increase of frequency.