With the rapid development of space technology and superconducting technology, the electrical characteristics of insulating materials at cryogenic temperature has become an important factor which influences the operating performance and reliability of power equipment and has attracted extensive attention. In this paper, a new test system for testing low temperature electrical characteristics of dielectrics has been developed. The temperature in test area is adjustable from 77K to 300K. The highest voltage is up to 30kV DC voltage and various atmospheric conditions such as vacuum, low pressure, etc. can be achieved. In addition, considering polymer insulating materials has excellent dielectric performance and mechanical properties at the normal temperatures, ball plate electrodes have been designed and some breakdown strength testing experiments on the insulating properties of polymer insulating material at cryogenic temperatures have been carried out. Meanwhile, in consideration of the effect of temperature, we also have conducted the testing experimental under the temperature range from cryogenic temperature to room temperature.