The physical process of a single-stage planar-pulsed-inductive accelerator is investigated.Measurements include the waveforms of circuit current,capacitor voltage,plasma radiation intensity,and temporal plasma structure photos captured by a high-speed camera.Experiments are conducted under static ambient fill condition using argon as propellant.Varied values of capacitor voltage and gas pressure are compared.Further discussions quantify the EM interaction between circuit and plasma,as well as their energy deposition and current sheet acceleration.Based on the results of experiments,physical mechanisms of the initial ionization phase and the following acceleration phase are analyzed theoretically.