Abstract: To meet the demand for rapid, on-site radionuclide analysis and measurement in nuclear leakage risk areas, a radionuclide identifier and its associated spectral analysis algorithm scheme with low maintenance and manufacturing costs have been designed and implemented based on the principles of spectral measurement and analysis The. scheme encompasses several key technologies, including smoothing, peak searching, background subtraction, radionuclide identification, and passive spectral stabilization algorithms. Specifically, the smoothing algorithm employs the least squares method, and through optimized programming of computational functions, it can achieve up to 120th-order smoothing processing. The first-order derivative peak searching algorithm has been optimized, and the passive spectral stabilization is divided into two processes: warm-up and self-stabilization. The spectral array for passive stabilization and the measured spectral array are mapped to different storage spaces, effectively addressing the issue of peak drift that is difficult to identify under long-term or high-count-rate conditions. The portable radionuclide identifier was tested for its energy linearity and spectral stabilization functions, which performed well. Single-nuclide and multi-nuclide identification experiments were conducted using standard sources of ¹³⁷Cs, ⁶⁰Co, and ¹³³Ba, and the results demonstrated that the instrument can accurately identify radionuclides with reliable outcomes. This validated the effectiveness and practicality of the scheme, providing effective technical support for rapid radionuclide identification in nuclear leakage risk areas.