A procedure is on the use of guided light beam angle geometric modeling done to achieve uniform light effect can be verified through the SAE regulations, the use of graphics software (Unigraphics) do parametric design, and with the optical simulation software (Lucidshape) for luminous intensity of the light pipe. From the simulation results can be obtained, the luminous intensity of the light guides geometry and thickness will increase or decrease as a result changed. When doing incremental changes in geometry and tends to a certain value, then the guide beam of light leakage rate will be close to a given value, this geometry can be referred to as the critical angle. After this analysis, you can find a better guide beam geometry designed to achieve better uniformity of light effects and through regulatory approvals, reduce development costs and development time.