The project of recovery navigation in the Xiaoqing River has been started construction，among which the Jinjiayan Lock，the Wangdao Lock will become the first batch of locks with water-saving basins in China. According to the characteristics of the interconnection between the culvert of water-saving basin and the culvert of lock head for the Jinjiayan Lock，we analyze the possibility of direct water conveyance between the upstream or downstream approach channel and the water-saving basin，and propose the corresponding hydraulic calculation method. Based on the principle of considering both the filling time and the water-saving rate，we deduce the relational expression between the optimal time to open earlier the lock head valve and the time to close earlier the water-saving basin valve. The results show that the culvert layout of the Jinjiayan Lock makes the resistance coefficient of direct water conveyance relatively large and effectively limits the return flow. When the lock head valve opens no earlier than the optimal time，the change of the water-saving rate is tiny which can be estimated by the common formula，the influence of the culvert interconnection is negligible.