To understand the behavior of particles within optical traps, dynamic analysis of laser trapping is necessary. A mathematical model has been established, which examines all the forces acting on a particle such as trapping force, gravity, buoyancy and Stokes drag. A simulator has been developed based on our mathematical model to define the motion of arbitrary shaped particles exerted primarily by trapping force and optical torque. The movement behavior of a designedtool made of silica trapped in air was predicted and the results showed that high rotation speed can be achieved when the torque produced by the laser beam is balanced by the drag torque exerted by the surrounding air. This gives a good verification that designed-tool made of silica or diamond trapped by laser beam can be used for nano-meter machining.