After Xiangjiaba ship lift is put into trial navigation，due to the poor matching between the actual navigation of 1 000 DWT ships in the lower reaches of Jinsha River and the main scale of the designed ship，the loading rate of the ship is low. To improve the traffic capacity of ship lift and the economic benefit of ship transportation，it is very necessary to carry out prototype observation of ship draught and gradually release the control standard of ship draught. Through prototype observations of entering and leaving the chamber of a large number of ships with different draughts and speeds，some factors about the draught control standard，such as the fluctuation of channel water level，water depth variation of ship chamber，speed and sinkage of ships entering and leaving the ship chamber，are systematically analyzed. The results show that there is still a safety clearance of more than 30 cm even if the ship draught is raised to 2.4 m.