The invention provides a tester for testing measurement accuracy of a PMU (Pressure Measuring Unit). The tester comprises a processor module, a D/A (Digital/Analog) conversion module, an electronic switch module, a power amplifier module and a decoder module. A B code time tick outputs a clock synchronization signal to the processor module through the decoder module; the processor module outputs a D/A control signal to control the D/A conversion module to output a direct voltage signal and an alternating voltage signal; the processor module outputs a switch control signal to control the electronic switch module to be switched on or off; the direct voltage signal outputs an analog key phase pulse signal through the electronic switch module; the power amplifier module comprises a driving power amplifier and a switching power amplifier; the alternating voltage signal is amplified through the driving power amplifier to output an analog machine end voltage signal; the analog machine end voltage signal is converted into an alternating current signal through the switching power amplifier; an analog machine end current signal is output. The invention also provides a method applying the tester to test the measurement accuracy of the PMU.