Abstract: Underwater weightlessness simulation,developed overseas from the 1960s, is an indispensable training methodfor astronauts on the ground. Theoretical basis of this method is thedynamics of the underwater weightlessness simulation, which can provide thetheoretical direction and the practice support. There are certain inherentproblems in this method, such as the water drag, deviation between thecenter of gravity and the center of buoyance, the change of the buoyance,and so on. Consideration of these factors in the application is necessary toattain a high-fidelity simulation. The theoretical analysis, mathematicalsimulation and physical test are the useful ways, which can indicate theunderlying principles for the underwater weightlessness simulation, answer thetheoretical problems in practice and provide effective measures to attain high-fidelity simulation results.This article provides a schematic introduction on theunderwater weightlessness simulation, outlines the developingbackground, basic principles, progresses, advantages and disadvantages ofunderwater weightlessness simulation, summarises the currentresearch of dynamics of underwater weightlessness simulation both in Chinaand abroad, and finally points out the trends of dynamics researchfor underwater weightlessness simulation in the future.