Based on principle of optical,Ray tracing method was used to set up model,which contained a parallel light deflection angle alpha and lens focal length and light intensity distribution of optical. In order to simulate the different parallel to the deflection angle of the incident light, to get the focus spot location distribution of light intensity on the focal plane and determining the focal spot position change and the size of the focal length and light intensity distribution of properties further.The results show that the incident light paralleled to the main axis centralized in flare area,uniform intensity distribution, and along with the increase the anger of alpha, the greater the focal spot center location deviated from the main optical axis. and the light intensity distribution of the focal spot area is not uniform, for designing a cylindrical probe need to determine the height of the cylinder and the radius parameter provides reference.