Being a good reflector, the human body can be recognized with the variation of radio signal. In this work we would show how this can be possible by a sequence of methods. First, we create a wireless sensor network (WSN) in a closed surface area and then we monitorthe variation of the signal in that surface in presence of human being. In additionwe monitor the radio signal also for the gesture movement. The variations are recorded by received signal strength indicator (RSSI). We then develop another human activity recognition system using radar and compare the accuracy for the two adopted systems. Some interesting results have reported in thepaper.