To solve the difficult problem of microwave amplifier hot network parameters measurement, advantages and disadvantages of the traditional loadpull method and the cold measuring method by VNA are analyzed, and a method of microwave amplifier hot network parameters measurement at output port based on dualsource VNA is given. By setting the two source of a VNA to keeping the tiny offset of working frequency and testing frequency, the hot network parameters at output port can be measured directly with a traditional dual port calibration. Matters needing attention are given, and the method has been applied to the domestic VNA products.