Abstract: A downburst event triggered by the merger of two convective cells occurred in Ningbo, Zhejiang Province on July 17, 2022. To better understand the formation mechanisms of downbursts in multi-cell storm environments, particularly those initiated by convective cell merging, a detailed analysis was conducted using sounding data, minute-resolution automatic weather station (AWS) observations, dual-polarization radar data, and dual-Doppler wind field retrievals. This study focused on environmental conditions, storm evolution, and the downburst generation process during the cell merger. The results are as follows. (1) At the Tangtou AWS, located within the downburst downdraft region, a sharp pressure rise, temperature drop, heavy rainfall, and peak wind gusts up to 33.7 m·s⁻¹ were recorded. Simultaneously, the Qifeng AWS, situated in the outflow zone near the incident site, registered gusts of 30.1 m·s⁻¹, with peak timings of various elements being well consistent with those observed at Tangtou. (2) The multi-cell storm system propagated northeastward. Before the downburst, a cell on the northern side intensified, exhibiting a strong updraft and a distinct Z_DR column indicative of vigorous lofting of moist air. As the southern cell approached, its upper-level outflow and cold downdraft suppressed the northern cell's development. Eventually, the merger of the two cells triggered a collapse at the cloud top of the northern cell, initiating a strong downdraft. (3) This downdraft was further enhanced by precipitation loading, melting and evaporation of ice particles, entrainment of dry and cold mid-level air, and cyclonic rotation. The resulting intense divergent outflow directly caused the severe surface wind event. This event indicates that during the merger of neighboring cells in a multi-cell storm, if the target cell exhibits rapid cloud-top collapse and a descending strong echo core, a downburst should be warned. Special attention should be paid to the suppression effect of upper-level outflow from an upstream cell on the target storm, providing a key precursor signal for ground high-wind warnings.