Given the good electrochemical performance and excellent irradiation stability of two dimensional transition metal carbides (MXenes), the development of MXene-based electrode materials for radionuclide detection is very promising. In this work, Ti₃C₂T_x MXene was activated via an alkalization strategy to form K⁺ intercalated Ti₃C₂T_x (K-Ti₃C₂T_x). Then the modified electrode of K-Ti₃C₂T_x/GCE was prepared on glassy carbon electrode (GCE). Ti₃C₂T_x and K-Ti₃C₂T_x were characterized by XRD, SEM and XPS techniques, and the electrochemical detection performance of K-Ti₃C₂T_x/GCE for trace uranyl ion (UO₂²⁺) was further investigated. Cyclic voltammetry (CV) experiments showed that the electrochemical response of K-Ti₃C₂T_x/GCE modified electrode to UO₂²⁺ increased significantly. Under the differential pulse voltammetry (DPV) scanning at pH 4.0, the K-Ti₃C₂T_x/GCE modified electrode presented a good linear detection relationship for UO₂²⁺ in the uranium concentration range of 0.5-10mg/L. The detection limit of this method is 0.083 mg/L (S/N = 3), with decent stability and repeatability.