The optimization of temperature field and the flow field is an important problem in the design and research of semiconductor cold box, but the optimization research can not be carried out by simple algebraic equations, nor can it completely rely on the experiment, because many sensors need to be arranged through the experimental measurement, which will destroy the flow field. Therefore, this paper adopts the numerical simulation method to study the best location of the cold end to optimize the temperature field and flow field distribution of the semiconductor cold box.