During the research and development of marine multi-shaft gas turbine, the axial force on the thrust ball bearing of the rotor is required to be measured under actual operating conditions, and then the axial force would be adjusted to a predetermined range with a predetermined method, so as to assure the bearing’s long-term and reliable operation. Basing on the theoretical analysis and engineering practice, we propose a practical method for the analysis and adjustment of the axial force. The method features combining the analysis of the air system and the small deviation analysis for the gas turbine engineering, with the typical experimental verifications. According to this method and the first measurement results of the axial force, the adjustment measures, which would locate the axial force value in a predetermined range, can be given. Since the proposed adjustment measures are based on the theoretical analysis, the component tests and the actual measurement for the whole engine, the result is of engineering accuracy. The engine delivery tests also show that the adjusting workload of axial force can be reduced significantly by use of the above method.