Thunderstorm downburst is a sort of outburst strong wind on or near the ground, and its wind field characteristics are significantly different from boundary layer winds. The study on its effect on the structures was relatively rare, nevertheless numerous structural failures around the world caused by thunderstorm were found. Computational fluid dynamics (CFD) was employed for this stationary downburst simulation, also the wind pressure distributions of the curved-roof in this flow had been surveyed by varying the parameters of the structure. The results show that the wind attack angle has significant effect on the wind pressure of curved-roof, so does the ratio of the rise to span. The predominant impacts of the ratio of wall height to span and the roof span were found at the windward side. Furthermore, by locating the roof beneath the downburst jet, the wind pressure distribution of the roof was also investigated to reveal the significant effects caused by vertical wind of downburst.