Poly(lactic acid) (PLA) is regarded as a promising biodegradable material with good application prospect. To further improve the comprehensive properties of PLA, 3-aminopropyltriethoxysilane (APTES) was used to modify the halloysite nanotubes (HNTs) to obtain the modified halloysite nanotubes (mHNTs), which was then used as nanofillers and melting blended with PLA matrix to prepare the PLA/mHNTs nanocomposites. The mechanical performance, thermal behavior, and the crystalline property of the nanocomposites were investigated. It was found that the mHNTs dispersed well in the PLA matrix, and compared to the pure PLA, the tensile strength of the prepared nanocomposites was improved by 33% and the crystalline degree was increased by 10.5%, respectively.