Abstract: Based on the Visual C# language, this article designed calculation software for 25 Hz phase sensitive track circuit. On the basis of testing the parameters of track circuit equipment, the software constructed the fourterminal-network-model using the theory of uniform transmission line, calculated the track circuit for normal state and shunting state, obtained all the equipment input and output voltage, power adjustment, shunt and other information in the condition of adjusting state, adopted exhaustive method to estimate the ballast resistance of track section. The calculation results were verified through the standard atlas of contrast and indoor test, the result was accurate.