Typhoon Lekima and Typhoon Rumbia are two tropical cyclones that caused severe disasters in Shandong. Based on multi-source observations and NCEP/NCAR reanalysis data, the two typhoon-induced extreme rainstorms in Shandong since the meteorological records began are compared and analyzed. The results are as follows. (1) Both processes are triggered by the interaction between typhoons and westerly troughs, resulting in extremely heavy precipitation. However, during Typhoon Lekima, the direct coupling of the westerly trough with the typhoon, combined with thicker warm cloud layers, stronger water vapor flux and its convergence, results in more intense precipitation. (2) Both typhoon rainstorms exhibit nearly vertical frontal zones of θse energy and secondary circulation systems associated with fronts. Typhoon Lekima features larger θse values, broader and thicker frontal zones of energy and nearly twice the vertical ascent velocity of Typhoon Rumbia. The topography significantly amplifies the two typhoon rainstorms. (3) The coupling between the larger vertical helicity and the frontal zones with higher temperature and humidity jointly promotes strong updrafts, and the intensity of the center is indicative for the future 6-h precipitation. The downward shift of the center of positive vertical helicity may indicate the weakening of precipitation. The maximum vertical helicity during Lekima reaches 5 times higher than Rumbia. (4) The vertical velocity of wind profiler radars v≥2 m·s^-1 can serve as a threshold for precipitation during the two typhoon processes. Vertical velocities commonly exceed 8 m·s-1 during heavy precipitation, while Typhoon Lekima exhibits greater vertical velocity.