The aim of this thesis is to analize the light field radiated from the LED collimator based on the free form secondary optics. It also discusses the thermal distribution cased by different type of heat sink design. The free form collimator can be divided into two parts: the reflection and refraction sections. By the helps of light distribution simulation tool, we can see how light field affected by the start point. For real application, we got an approximate scale of start point length with LED’s size. It gives an idea how to choose the start point of free form collimator to reach as high as 80.17% light collection. Heat sink is a critical point to enhance LED life time and stability of spectrum distribution. This thesis shows the evidence that based on the same power, thermal generated by multi-items LED is lower than that of single chip LED. Relationship between the LED’s geometry setting and its thermal distribution were also discussed.