In modern aerial warfare, the rapid evolution of advanced detection technologies has elevated the enhancement of stealth capabilities to a core priority in the research and development of high-performance combat aircraft.The aero-engine nozzle is the main source of the backward radar scattering characteristic signals of combat aircraft. Aiming at the problem that the traditional evaluation methods for the radar stealth performance of nozzles are not completely accurate, the iterative physical optics method was used to calculate and analyze the radar cross section(RCS) of the three different S-shaped nozzles: single S-bend, double S-bend, and multi-dimensional deflected S-bend building on monopulse radar detection theory, the detection range and detection probability of each nozzle were systematically analyzed under X-band and C-band radar illumination, within predefined detection angle ranges in both the elevation and azimuth planes. Key results indicate that under the specified radar detection conditions, the detection probability and detection range of the nozzles exhibit a strong correlation with the RCS fluctuation data. Specifically, under a given signal-to-noise ratio (SNR), the multi-dimensional S-shaped nozzle demonstrates the lowest detection probability in both detection planes under horizontal polarization. In the C band, the detection probability of the multi-dimensional S-shaped nozzle increases, while the double S-shaped nozzle exhibits a lower detection probability. When the detection probability is fixed, the multi-dimensional S-shaped nozzle consistently exhibits the shortest detection range in both X-band and C-band, confirming its superior stealth performance in reducing radar detectability.