An optimization design method of collimating lens is proposed. The quadratic B-spline theory, Scheme language and optimization engine are used in combination to achieve the optimization of freeform surface lens. The Lambert emission of 1 mm × 1 mm LED is used as light source, and the lens material is polymethyl methacrylate (PMMA). The collimating lenses of different structures are optimized by this way. The energy efficiency can be up to 90% . Compared with the current methods, it has the advantages of less dependence on the initial model, simple design process and high versatility.