Two methods are considered for choosing the values of the variable parameters of the digital stabilizer for a non-stationary object, which ensures the invariance of the closed stabilization system to the action of external disturbances. The comparative analysis of the considered methods was carried out in order to identify their advantages and disadvantages. As an example, it is considered the problem of parametric synthesis of the digital stabilizer of the C5M cosmic stage of the Cyclone-3 carrier rocket as part of the program for the modernization of these objects created in the late 70s by the joint efforts of the Yuzhnoye Design Bureau and NPO Hartron, which contain an analog stabilization system and operating to date. It is concluded about advisability to replace the C5M analog stage stabilizer with the digital stabilizer in order to improve the quality of the stabilized process of the stage in the active part of the flight trajectory. It is shown that both methods considered in the article lead to the creation of the digital stabilizer that provides a significant reduction in the static error of the closed digital stabilization system of the cosmic stage of the carrier rocket and an increase in the quality of stabilization process.