In order to real-time monitor the vibration state of the products during transportation, a hydrogel-based square triboelectric nanogenerator (S-TENG) was prepared using self-made high-strength and strong polyacrylamide/sodium alginate dual-network (PAM/SA-DN) hydrogel as electrode and a spring as trigger, and the output signal of S-TENG under different vibration states was tested. The experimental results show that the tensile strength of PAM/SA-DN hydrogel was up to 371.4 kPa, with the elongation at break of 547%. When the vibration frequency was 0.5 Hz, 1.0 Hz and 2.0 Hz, the required time for the S-TENG to output the peak voltage was 8.0 s, 4.1 s and 2.1 s, respectively. When the vibration amplitude was increased from 10 mm to 30 mm, the peak output voltage was increased from 9.0 V to 17.5 V. In addition, a platform was built to simulate the scenario of a car passing through speed bumps. The height and number data of the speed bumps were accurately obtained according to the output voltage signal. Therefore, the S-TENG has promising application potential in road transportation monitoring.