Mechanisms for lifting space rockets into a vertical position are complex and expensive elements of ground equipment. Under the same loads, depending on the rationality of selecting their geometric parameters, the mechanisms can significantly differ in cost and weight. At present, design considerations, enumeration and descent methods, or the graphical-analytical method, are used to select rational geometric parameters of these mechanisms, which, taking into account a large number of restrictions, makes the process of solving such engineering problems time-consuming and laborious. The paper describes a method for selecting rational geometric parameters for the lifting mechanisms of space rockets. The method is based on the analytical solution obtained by the authors of the equations for changing the load in the initial and final position of the rocket lifting, depending on the initial installation angles of the drive element of the mechanism. Under given parameters of the load on the lifting mechanism in most practically important cases, the method makes it possible to obtain rational values of the main geometric parameters of the lifting mechanisms without the enumeration and descent methods. These parameters include the distances between the joints and the initial angles of installing the elements of the mechanism. If a hydraulic lifting drive is used, the method makes it possible, if necessary, to choose the rational basic parameters of the hydraulic cylinders. The method developed can be used in the design and modernization of mechanisms for lifting space rockets.