With the development of aerospace technology, new deep space probes will encounter two special operating conditions during takeoff: the magnitude and direction of the engine thrust vector changing over time; the direction of gravity during the initial launch does not coincide with the main axis of the spacecraft. During the flight, liquid fuel will be continuously consumed. This article suggests a new solution for the problem of liquid sloshing in spacecraft storage tanks to the aforementioned three working conditions: taking into account the impact of spacecraft translational acceleration during the dynamic modeling stage and then analyzing the sloshing situation of thrust not along the spacecraft axis direction; calculating the liquid sloshing problem under variable charge to liquid ratio conditions using the method of variable equivalent mechanical model parameters; and simulating the situation where the liquid level is not perpendicular to the tank axis when the tank tilts by setting an initial swing angle for a single pendulum in the equivalent mechanics model. This article takes the Cassini storage tank as an example to calculate the sloshing force and moment under the three working conditions mentioned above in a semi filled state. Finally, taking a certain type of spacecraft liquid storage tank as an example, sloshing analysis is carried out under actual launch conditions. The practicality of the calculation approach presented in this article is confirmed by the calculation results, which are in good agreement with the results of calculations made using commercial software Flow-3D.