The work aims to explore the corrosion mechanisms of PCB-HASLs under typical molds in tropical rainforest. The PCB-HASL samples were sterilized and placed in a cabinet for outdoor exposure for 2 years in Xishuangbanna. The corrosion behaviors of samples taken back from different periods were observed. The selected typical molds spores were sprayed on sterile samples and placed in a hot and humid environment. Morphology, composition and growth of molds were observed and analyzed by laser scanning confocal microscope (3D LSCM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The surface potential of the PCB-HASL samples under different types of molds in different times were analyzed by electrochemical workstation and scanning kelvin probe (SKP). With the increase of exposure time in the outdoor, the corrosion area of the PCB-HASL gradually increased. The surface potential of the PCB-HASL increased at first and then decreased. The results of EDS showed that the corrosion product mainly contained 58.88% of Sn and 30.93% of O, and the corrosion product was mainly oxide of Sn. Corrosion beneath the coverage of Fusarium equiseti and Daldinia eschscholtzii was serious. Fusarium solani grew vigorously which caused a significant reduction of corrosion potential from －0.3 V to －0.52 V in the mid-term. The typical molds having significant effects on the corrosion processes of PCB-HASL in the rainforest of Xishuangbanna are Fusarium equiseti, Daldinia eschscholtzii and Fusarium solani, which can corrode the PCB-HASL in such a hot and humid environment. The corrosion mechanism is mainly the electrochemical corrosion under the thin liquid film.