The present invention proposes a ground simulation device for plasma environment in adjacent space and its simulation method. The simulation device includes a vacuum system, a drawable vacuum microwave anechoic chamber system, a plasma beam generation system, an air intake system, a water cooling system, and an excitation power supply. system, vacuum pump group system, target blunt body system, microwave anechoic chamber support system, target blunt body support system, plasma parameter diagnosis system, microwave transmission measurement system, miniaturized antenna group system and central control system; Realize the electromagnetic communication measurement of the plasma environment, check the plasma parameter diagnosis through different diagnostic methods, and generate a plasma beam with high purity, adjustable plasma density and beam size in a long period of time; more Realistically simulate the near-space plasma environment, and provide microwave transmission measurement and plasma diagnosis methods required for relevant research in this environment.