This paper takes the full-ocean-depth sampling device of the mechanical hand-held sampler as the research object, simulates the soft viscous sediment as non-Newtonian Herschel Bulkley viscoplastic fluid, uses the finite volume method and applies the computational fluid mechanics software Fluent to establish the sediment sampling model.VOF method is used to track multiphase flow interface. The effects of the sampling speed, diameter of the sampling tube, drainage discharge and sediment dynamic viscosity on coring rate and sampling volume are studied. The results show that the sampling volume is negatively correlated with those influencing factors. However, the coring rate decreases with the increase of sampling speed, drainage area ratio at inlet and outlet, and dynamic viscosity of sediment. The coring rate first increases and then decreases with the increase of the diameter of the sampling tube, and the peak value is related to the sampling speed and tube diameter. Then, based on the analysis of the numerical simulation results, a sampling simulation experimental platform is built and the sampling experiment is carried out. It can be concluded that the simulation results tally with the experimental results, with the maximum error being only -4.6%, which further verifies the correctness of the numerical model.