Recent years have seen significant advancements in the field of road vibration energy harvesting using piezoelectric technology, including the watt-level road piezoelectric energy harvesters (RPEHs). However, research on the fatigue life of RPEH under thermal-mechanical coupling effect is lacking. In this study, six lead zirconate titanate (PZT) block piezoelectric transducers with distinct properties were fabricated, and five transducer structures were compared. The effects of piezoelectric material properties, pavement temperature, and transducer structure on RPEH fatigue degradation were investigated using approximately 23 million mechanical loads. The findings revealed that the output power of the soft PZT was significantly greater than that of the hard PZT under low-frequency cyclic loading. However, the Curie temperature decreased with an increasing piezoelectric constant of the soft PZT. Therefore, the stability of the output voltage worsened as the ambient temperature approached half the Curie temperature. Specifically, when the ambient temperature was 50 °C, the output failure phenomenon readily occurred during the initial stage of fatigue loading. By optimizing the transducer structure, the fatigue characteristics and high-temperature failure phenomenon of RPEH could be effectively improved. The coupling output modes of d ₃₃ and d ₃₁ were superior to that of the d ₃₃ mode. Among these, the drum transducer exhibited the highest output performance and operational stability across different ambient temperatures, excitation frequencies, and displacements. After six million intermittent loads over 15 d (equivalent to two years of traffic load), the output power decreased from 6.51 to 6.02 mW with a degradation rate of merely 7.53%, indicating a promising application prospect. The results provide an crucial design foundation for the entire life cycle operation of RPEH in road engineering.