Here, a type of metal–organic frameworks (MOFs) of microsphere modified Ag nanoparticles (Ag NPs), Ag@Ni3(BTC)2, was prepared through a feasible one-pot hydrothermal reaction, followed by characterization with XRD, FT-IR, SEM, HRTEM, XPS and BET. The doping modification of Ag NPs can effectively improve the conductivity of MOFs, and it has remarkable electrochemical performance as electrode material in supercapacitors and electrochemical sensors. The as-prepared Ag@Ni3(BTC)2 composites show a high performance of 983.0 F/g at 1 A/g with excellent cycling stability and rate capability. Moreover, the electrochemical behavior of the Ag@Ni3(BTC)2 nanocomposite toward Pb(II), Cu(II), and Hg(II) was investigated using differential pulse anodic stripping voltammetry technique. The optimization of operational parameters, such as pH, deposition time, and deposition potential was performed to detect trace levels of metal ions. The results indicated a potential application of Ag@Ni3(BTC)2 as electrode material in supercapacitors and electrochemical sensors.