Abstract: In order to improve the sampling rate of gravity sampler, this paper simulated the free falling posture among a wide range before its grounding based on OpenFOAM and dynamic overset grid method. The accuracy and feasibility of this method have been verified by calculating free falling of a sphere and comparing the results with literature. Established two-dimensional time-domain coupled calculation model of the sampler which interacts with flow field and simulated the free falling posture with initial slant angle of 0°, 5°, 8°, analysed the relationship among falling distance, falling speed and slant angle of the sampler. In the end the influence on sampling rate made by slant angle of the sampler has been discussed. The numerical results show that the initial slant angle has a great influence on falling posture and sampling rate. All of the data and conclusion can provide measurement with guidance.