The Reactive power compensator and monitor of Power factor system is designed based on ARM7, with function of long distant transmission. It monitors and measures alternation current parameters, such as the active and reactive electric energy, active and reactive power, voltage, current, power factor and other parameters. To realize reactive compensation, it can automatically switch shunt compensation capacitor by Thyristor Switch Capacitor. The result can display via LCD. Moreover, the system has anti-power-down and code protection.