In this paper, we optimized and simulated the heatsink of 75W LED module for street lighting and evaluated the optical properties with the manufactured heatsink. the structure of LED package make simple as chip and heatslug and thermal flow is analyzed by using the FEM(Finite Element Method) with CFdesign V10. Also, we measured the temperature of heatsink and evaluated the optical properties with infrared thermal image camera and integrated sphere system for luminous flux in $1;[m^3]$ box. As results, Heatsink optimized in 3 mm pin thickness, 6 mm base thickness and 16 number of pin count by using Heatsink-designer and got the results which is the temperature of $47.37;[^{circ}C]$ and thermal resistance of $0.48407;[W/^{circ}C]$. In thermal flow simulation, the temperature of heatsink decreased from $51.54;[^{circ}C]$ to $51.51;[^{circ}C]$ and the temperature of heatsink by the time in real measurement decreased from $47.03;[^{circ}C]$ to $46.87;[^{circ}C]$. Moreover, we improve 0.68 % in the decreased ratio of the luminous flux.