The heat dissipation performance of the junction boxes is directly related to the service life of solar modules. In this paper, the PT100 thermocouple and the MT2 infrared thermometer is used to conduct a preliminary study on the heat dissipation performance of different models of junction boxes. We selected three types of junction boxes from different manufacturers, and then produced a piece of laminating module without solar cells, using a piece of toughened glass which size is 1574*802*3.2mm, two-tier EVA film, and a sheet of TPT as the substrate. Junction boxes filled with silica gel A, silica gel B and no gel were fixed on the laminating module, which is a simple procedure on producing PV modules at present, and were evenly spread. All the junction boxes were connected in a series circuit. When every thing ready, we enforced respectively 5A and 8A DC current on the circuit for 5 hours apiece, and the environment temperature 25 °C was maintained. Simultaneously we tested the temperatures of the boxes inside and outside hourly. The investigation indicates that junction box filled silica gel shows better performance.