Abstract: This study investigates the raindrop size distribution (DSD) characteristics of the extreme rainstorm that occurred on September 7-8, 2023, in Shenzhen (hereinafter referred to as the “9·7” rainstorm), based on DSD observation data from Shenzhen FuTian station. The characteristics of key DSD parameters for different precipitation types were analyzed, and the contribution of different raindrop size levels to the rain rate was evaluated from the aspect of temporal evolution. The results show that the convective precipitation during the “9·7” rainstorm is well consistent with the characteristics of “maritime” types. Compared with rainstorm cases from other regions, the DSD in this rainstorm is characterized by smaller raindrop particle sizes and higher number concentrations. The normalized intercept parameter (N_w) of stratiform precipitation is higher than that recorded in other regions of China, while the mass-weighted mean raindrop particle size is equivalent to that observed in other regions of Guangdong Province. The mechanisms of precipitation rate enhancement differ between precipitation types: convective precipitation is primarily due to an increase in raindrop number concentration(N_t), while stratiform precipitation is driven by both N_t and D_m. Regarding the contribution of raindrop sizes, medium-sized raindrops dominate the precipitation rate, accounting for approximately 50%~95% during the peak rainfall period (from 14:00 to 22:30 UTC on September 7). While variations in precipitation rate are closely related to the contribution of large raindrops, with a correlation coefficient of 0.820. When precipitation rate increases, the fractional contribution from large raindrops rises rapidly, with the increase in number concentration playing a critical role. Namely, the increase in R is accompanied by the growth of raindrops toward larger particle sizes. Further analysis reveals a systematic pattern in the fractional contribution of different raindrop sizes with varying precipitation intensity: as precipitation rate increases, the contribution of large raindrops rises steadily, that of small raindrops declines, while the contribution of medium-sized raindrops first increases and then decreases.