The invention provides a device and a method for plasma etching process treatment. The method includes alternate circulating deposition and etching process sub procedures. In each sub procedure, a time control module controls opening and closing of a first gas transmission valve or a second gas transmission valve, gas in the sub procedure is transmitted into a process cavity, a detection unit of a detection module detects a characteristic value formed by the concentration of the gas in the process cavity, the type and the concentration of the gas are determined according to the characteristic value, and a switching unit of the detection module judges whether the characteristic value reaches a preset threshold value, and switches a grid bias power supply to output bias power meeting the sub procedure if the characteristic value reaches the preset threshold value. Gas transmission and bias power switching are controlled by the time control module and the detection module respectively, bias power switching time can be more accurately controlled by the detection module for monitoring, the shortcoming of non-synchronism caused by different delay time in gas transmission and bias power switching is overcome, and stability and controllability of the whole process are improved.