The influence on the motion of single solid particles in a Newtonian fluid by melting and convection was directly simulated. The fluid motion was computed from the conservation laws. Density and viscosity change with the fluid temperature, the particles move according to the equations of motion of a rigid body under the action of gravity and hydrodynamic forces arising from the motion of the fluid. In the process of melting, a distinctive morphology develops due to the different heat flux around the particles surface, and the thermal gradient determines the melting rate. The phases were coupled by the fluid-particle mutual force, force moment and the boundary conditions. In our study four different situations were considered, namely the sedimentation in isothermal fluid without thermal convection and melting, sedimentation in cool fluid and hot fluid without melting, and sedimentation with thermal convection and melting. The results showed that the vortex shedding arising from the natural convection changes the sedimentation velocity and induces horizontal oscillating.