In order to more accurately reflect the sources of uncertainty in the measurement process of the rise time of step signals and improve the credibility of measurement results, numerical simulations and experimental analyses were conducted on the uncertainty components of step signal rise time measurement introduced by noise. The results indicate that the signal?to?noise ratio significantly influences the uncertainty of rise time measurements. In situations with low signal?to?noise ratio, the uncertainty in rise time measurements caused by noise becomes the main source. By comparing the application effects of the Savitzky?Golay smoothing algorithm and the moving average smoothing algorithm in the calculation of rise time for step signals, it was found that the use of an appropriate smoothing algorithm can reduce the uncertainty components introduced by noise, with the moving average smoothing algorithm showing better performance. This study contributes to improving the reliability and accuracy of dynamic signal measurement results, and is of significant reference value for uncertainty analysis in dynamic signal testing in the fields such as aviation, aerospace, and automotive industries.