The transversal and longitudinal intensity and phase distribution of speckle fields in diffraction patterns of random scattering surfaces under vortex beam with different topological charges are simulated. It is observed that the transverse and longitudinal average size of speckle grains is smaller than that of speckle grains produced by Gauss beam passing through the random scattering surfaces, and it becomes smaller with the increase of the topological charge and radius of vortex beam. At the same time, the density of phase vortices becomes larger with the increase of the topological charges and radius of vortex beam in the diffraction region. The speckle sizes can be adjusted by changing the topological charges and radius of vortex beam to trap particle. This result can be used to reduce the noise.