Abstract: External pressures on the surfaces of principal building were obtained by a series of wind tunnel tests on rigid models. Acceleration responses of the principal building were calculated at different reduced velocities. Envelope interference factor (E_IF) distribution and vortex-induced vibration mechanism of the along-wind peak acceleration were detailed studied in different breadth ratios B_r (B_r=B_i/zB_p) and height ratios H_r (H_r=H_i/H_p). Furthermore, correlation analyses were carried out for the envelope interference factors E_IF in different breadth ratios B_r and height ratios H_r. Results show that the maximum values of E_IF are 2.3 and 2.06 when B_r equals 0.4 and 0.6 respectively, because of the influence of vortex-induced vibration. In wind resistant design process, the amplification effect of along-wind acceleration should be paid more attention when B_r is small. In non-resonance cases, the remarkable amplification region becomes larger with the increase of B_r, and the corresponding maximum values of E_IF also gradually increase. Correlation coefficient of E_IF between H_r=1.2 and 1.0 is up to 91%, and the distribution of. E_IF nearly keeps unchanged when H_r ≥ 1.2.