Abstract: The gust generator is the key equipment for the wind tunnel test in response to the gust. According to the operating characteristics of the oscillating vanes gust generator, a simplified steady vortex theory is used to deduce the calculation formula of the Y-direction wind speed in the downstream flow field of the gust generator. With the experimental researches done in the 0.55 m × 0.4 m low-speed wind tunnel (a pilot acoustic wind tunnel), the influences on the extreme wind speed of the gust flow field were systematically studied by changing the design parameters of the gust generator (vane chord length, number, spacing) and operating parameters (vane swing amplitude, swing frequency, incoming flow velocity). The research shows that the simplified formula derived in this paper can explain the changing mechanism of the Y-direction wind speed in the downstream flow field after the design and operating parameters of the gust generator are changed. The gust flow field generated by the gust generator can be simply analyzed during the design of the gust generator. To increase the Y-speed extreme value of the downstream flow field of the gust generator, increasing the number of vanes has an advantage over increasing the vanes chord length. Before the vanes stall, the larger Y-speed extreme value can be obtained by increasing the vanes swing speed rather than by increasing the vanes swing frequency. The spacing of the vanes for the gust generator should not be too small, otherwise the equivalent lift coefficient of the vanes would decrease. When the vanes spacing is 1.2 times the chord length, the maximum Y-direction wind speed can be obtained. This research can provide reference for the design of gust generators in other wind tunnels.