The invention provides a ro-ro passenger ship inclining test method. The method includes the steps that equipment and tools used for a test are arranged, two sets of balancing weights needed for the test are arranged on larboard and starboard roll-roll shipment decks of a ro-ro passenger ship according to the width of the ship and placed in the positions close to ship boards, the transverse inclination of the ship is set to be within the angle of 1.5 degrees, and according to a ship statics formula, the transverse inclination angle of the ship is predicted as the formula shown in the patent; the swing amplitude of a cycloid is measured; and a test process is conducted, the balancing weights are placed according to the placing sequence, the test is conducted repeatedly, nine units of data are obtained, and the inclination angle of the ship is elicited from the formula. The method has the beneficial effects that test time is saved by the application of the method, following constructionadjustment is facilitated, and the use rate of a crane and a tug is increased. Under the condition that two ships are moored in the same berth, the ship not included in the test does not need to be dragged out of a wharf, and conditions are created for underwater construction of the ship. The data adopted in the method are accurate and reliable, the process is simple and convenient to conduct, a construction tool is operable, the method can be adopted in a series of ships, and production efficiency is improved.