Due to the small cross-section coefficient of a shiplift chamber, the hydraulics problem becomes a complex water flow problem in ship operation. To prevent the ship from touching the bottom and ensure the safety of ship navigation and the docking of the chamber, a generalized physical model was used to study the ship squat of a 1000 t ship leaving the chamber. Throughout the experiment, the law of variation law in the ship squat under different chamber widths, water depths, chamber lengths, ship speeds and ship starting acceleration was obtained. In this study, the flow pattern of the ship leaving the chamber was divided into two parts: backflow and bottom flow. According to sensitivity analysis, when the shipping speed was less than 0.9 m/s, the influence of the width of the chamber on the squat was greater than that of the depth of the chamber; when the speed is greater than 0.9 m/s, the influence of the depth of the chamber on the squat was slightly greater than that of the width of the chamber. Based on our theoretical analysis, the basic expression of a ship squat was established.