Flexible wearable electronics have garnered substantial attention as promising alternatives to traditional rigid metallic conductors, particularly for personal health monitoring and bioinspired skin applications. However, these technologies face persistent challenges, including low sensitivity, limited mechanical strength, and difficulty in capturing weak signals. To address these issues, this study developed a hierarchical sandwich-structured piezoresistive foam sensor using phase inversion and NaCl sacrificial templating methods. The sensor exhibits an exceptional sensitivity of up to 83.4 kPa⁻1 under an ultralow detection pressure of 2.43 Pa. By optimizing the foam porosity, its mechanical performance was significantly enhanced, reaching a tensile fracture elongation of 257.3% at 73.42% porosity. The hierarchical sandwich structure provided mechanical buffering and layer-enhancement functionalities for dynamic responses, whereas the nanostructure further refined signal acquisition and interference resistance. Signal analysis using discrete wavelet transform (DWT) and continuous wavelet transform (CWT) enables multiscale and multifrequency characterization of arterial resistance signals under varying applied pressures. These findings underscore the sensor’s ability to capture weak signals and analyze complex pulse dynamics. This advancement paves the way for the extensive application of multifunctional sensors in smart devices and health care. This method offers a robust scientific basis for further understanding and quantifying arterial pulse characteristics.