The main purpose of the present research is to develop a tower-mounted high performance environmental control box. By the technology of throttle to change the flow rate of capillary cryogen, we can control evaporator's surface temperature to obtain constant temperature in the box. In order to accurately control operational temperature inside the box, the main purpose of the present research is to be environmental control box's dynamic system identification, then to be design and analysis of the control system. A prototype of high performance environmental control box using PIC16F877A was built and tested. The experimental results show that we can control the box temperature between 15~22℃ and the temperature control error is less than 0.8℃, otherwise, the 5W disturbance is under control.