Motions of a free-fall lifeboat have been classified into four categories by observations of model experiments. In this paper, these categories are examined quantitatively using a numerical simulation method that was developed by the authors. Furthermore, four parameters, i. e., angle of launching skid, sliding distance of a boat on the skid, fall height and guide rail length, are chosen as launching parameters, and the relationships of these parameters to the motion categories are investigated. As the results of numerical studies, zero horizontal velocity of the boat at water exit is found to be an effective criterion that identifies unfavourable motions of the free-fall lifeboat after water entry. Finally, using the CAR index proposed by IMO, acceleration exerted on the occupants of the boat during water entry is evaluated, and its relationships with the above mentioned velocity criterion, the launching parameters and the angle of safe seat for the occupants are discussed.