Among the various materials that are employed to enhance the electrochemical response of sensors, activated carbon (AC) compared to other similar carbon materials, such as graphene and carbon nanotubes, enjoys relatively more feasible preparation and practical applications [1,2]. It is important to provide environmentally friendly, affordable and efficient carbon materials. Results: Herein, Cu-BTC metal organic framework was prepared through one-step solvothermal method. Moreover, an available and cheap biomass called eucalyptus bark was used to prepare AC through carbonization and activation processes. Then, a simple electrochemical sensor was employed based on GCE modified by microporous AC and Cu-BTC (AC/Cu-BTC/GCE) for voltametric determination of phosalone as an organophosphate pesticide using differential pulse voltammetry (DPV) method. A high binding affinity can be observed between phosalone and Cu-BTC, which forms a barrier for electron transfer of Cu-BTC. Therefore, in the presence of phosalone, the number of active copper ions involved in the redox reaction decreases with the formation of the phosalone-Cu(Ⅱ) complex. Under optimal conditions, the mentioned sensor exhibited an ultralow detection limit of 6.94 × 10 -13 M and a wide linear range of 1.0 × 10 -12 – 1.0 × 10 -9 and 1.0 × 10 -9 - 1.0 × 10 -5 M. Also, different fruit juices including cherry, apple and peach and agricultural water were selected as real samples. Significance: Also, the prepared electrochemical sensor was studied in terms of repeatability, selectivity and stability and the results confirmed that the proposed AC/Cu-BTC/GCE can serve as an efficient electrochemical sensor for voltammetric determination of phosalone.