High-power light emitting diode (LED) develops greatly owing to its energy efficiency, light mono-direction and long operating life. But it is critical to have a secondary optics design for the LED street light, for obtaining good output efficiency and light distribution pattern. This article introduces many advantages of LED as street lightings source, and also analyzes the status and features of LED lamps’ application as street lightings. This article mainly designs a secondary optical light distribution implement using Lighttools 7.1. This paper also gives an example of one kind of freeform surfaces lens which can realize rectangular light shape.