With the rapid development of lighting technology and auto industry, it has been an important research subject for many motor manufacturers to improve headlight performance. LED light has achieved a dominant position in lighting technology because of the advantages, such as the small size, low energy consumption, and long service life. In a complex working environment, the reliability of light source module is an indispensable parameter for a LED headlight, which can lead to poor energy efficiency, decreased light intensity, and a shorter service life with low reliability. In the working process of headlights, the rising LED temperature will reduce the luminous flux and thermostability, even affect normal operation. Therefore, understanding and evaluating the relevant factors affecting LED reliability is an important measure to ensure the stabilizations of LED headlights. In this paper, the finite element software and optical simulation software are used to simulate the temperature field, flow field, and optics of the LED headlight module. Firstly, in order to understand the influence of temperature on the stability of the headlight, the temperature field and flow field distribution of the headlight are studied by finite element software. Secondly, we use the optical simulation software to study the optical parameters of headlight at different temperatures. It shows that the highest temperature appears in the LED chip, and the lowest temperature appears in the maximum end face of the headlight shell. For the same power LED, the higher working temperature leads to higher LED junction temperature. Affected by the working environment temperature, the luminous flux of the headlight will decrease with the increase of temperature.