Based on the high resolution data of the wind speed and direction，as well as the wind pressure data measured from an instrumental gable roof of a low rise building during the tropical storm of Mujigae, the influences of vertical wind angles on the roof pressures of the low-rise gable roof building are investigated when the incident flow is perpendicular to the ridge line during tropical cyclone. The results show a clearly linear relationship between the non-conventional pressure coefficients and incident vertical wind angles. As the distance between pressure taps and leading edge increases, the non-conventional pressure coefficients affected by the incident vertical wind angles decrease. In addition, due to the influence of the ridge, leeward roof area that is close to the ridge is greatly affected by the incident vertical wind angles. The incident vertical wind angle may be one of the main causes for the discrepancy between the experimental pressure coefficients and field measurements near the leading edge and the ridge. Therefore, the influences of the incident vertical wind angles should be considered in the wind tunnel tests.