A monitoring circuit and a monitoring system for electro-static discharge (ESD) protective device are disclosed herein. The monitoring circuit includes an oscillating unit, a signal processing unit and a comparator. The oscillating unit includes a first monitoring end and a second monitoring end. The first monitoring end is configured to be electrically connected to an ESD protective device. The second monitoring end is configured to be electrically connected to ground. When the first monitoring end is not electrically contacted to a user’s body or the second monitoring end is not connected to ground, the oscillating unit is configured to output an oscillating signal. The signal processing unit is electrically connected to the oscillating unit, and is configured to output a first voltage according to the oscillating signal. The comparator is configured to compare the first voltage and a reference voltage, and correspondingly output an alarm signal.一種靜電防護裝置監控電路及系統在此揭露。靜電防護裝置監控電路包括振盪單元、訊號處理單元以及比較器。振盪單元包括一第一監控端與一第二監控端。第一監控端用以電性連接靜電防護裝置。第二監控端用以電性連接接地線。在第一監控端未電性接觸使用者的身體或是該第二監控端未接地的情形下，振盪單元用以輸出振盪訊號。訊號處理單元電性連接振盪單元，並用以接收振盪訊號，且根據振盪訊號輸出第一電壓。比較器用以比較第一電壓與參考電壓，且相應地輸出警示訊號。
