As one of the most important supporting components, the lubricating performance of the water-lubricated bearing greatly affects the safe operation of the whole propulsion system. However, the lubricating performance of the water-lubricated bearing under low speed is difficult to be guaranteed due to the water film is difficult to form under such harsh conditions. Groove seem to be an effective means to improve lubricating performance and have been widely used. Unfortunately, the effect of the groove parameters on the lubricating performance of the water-lubricated groove bearing (WLGB) under low speed lacks of systematic reporting. Herein, a numerical model based on the average flow Reynolds equation was developed and verified. The effect of groove kinds (rectangular, triangle and cuneal), locations, sizes and amounts on the lubricating performance of WLGB under low speed was detailedly investigated. The results confirmed that the water-lubricated bearing without groove presented a poor lubricating performance under low speed. Additionally, the groove parameters highly influenced its role and the rectangular groove with suitable parameters could feasibly improve the lubricating performance of the WLGB. The load-carrying force of the rectangular groove bearing with suitable groove parameters was improved and the friction coefficient was decreased under simulated conditions. It is believed that this study will provide a theoretical basis for grooves selection of WLGB.