[Purposes] To promote the full mechanized construction of transmission line projects in complex environmental conditions such as plateaus, mountainous areas, and hilly regions, a lightweight precast component-assembled micropile foundation is proposed. [Methods] Its bearing performance was investigated through model tests and three-dimensional finite element simulations. [Findings] The results indicate that under uplift and compressive loading, the ultimate bearing capacity of the prefabricated micropile foundation reaches 93% and 91% of that of the cast-in-place foundation, respectively. Stress concentration occurs in the regions surrounding the connecting bolts and connectors. The vertical load is effectively transferred from the connecting bolts to the shear keys and subsequently to the connecting steel plates, forming a clear and well-defined load transfer path. The displacement distributions of the prefabricated and cast-in-place caps are similar, with the maximum displacement symmetrically located at the center of the cap bottom. Under uplift conditions, the relative differences between the maximum and minimum displacements are 1.15% and 1.16%, respectively; under compression conditions, they are 1.54% and 0.42%. [Conclusions] This study provides theoretical support and engineering reference for the mechanized construction of transmission line foundations under complex geological conditions.