Triboelectric nanogenerator (TENG) has the great potential to harvest the electrostatic energy and mechanical energy of raindrops. However, raindrops are small and scattered, and it is difficult to harvest their mechanical energy effectively. In this paper, a gridding triboelectric nanogenerator (G-TENG) with an area of 81 cm2 is designed and developed to effectively harvest the mechanical energy of raindrops on a large scale. Its peak output power density is 8.56 mW/m2, which is 245 times the value of 35 μW/m2 of a general TENG without gridding. Each unit of the G-TENG can work independently, which can effectively decrease the mutual counteraction of elastic deformation among the adjacent positions of the raindrop impacting layer and avoid the accumulation of raindrops. Under the impact of simulated raindrops from a shower at a flow rate of 0.137 mL/(cm2·s), the open-circuit voltage (Voc) and the short-circuit current density (Jsc) of the G-TENG reach 400 V and 2.5 mA/m2, respectively. The peak output power density reaches 110 mW/m2, which is 42 times the reported maximum value of 2.6 mW/m2 of raindrop energy harvesting TENGs with the size larger than 10 cm2. Moreover, the G-TENG can harvest the mechanical energy of raindrops at a wide range of raindrop flow rates from 0.055 to 0.219 mL/(cm2·s). This work contributes to the raindrop mechanical energy harvesting on a large scale.