Abstract: The surface modification of nano-lamellar hydroxyapatite (LHAp) was carried out with silane coupling agent (SC) and stearic acid (SA), separately. The unmodified and two modified nano-platelet hydroxyapatite (np-HAp) reinforced polylactic acid (PLA) (np-HAp/PLA, SC-np-HAp/PLA, and SA-np-HAp/PLA) composites were prepared by extrusion process. The microstructure, mechanical properties, thermal stability, crystallinity, and wettability of the three composites were compared. XRD, FTIR, XPS, SEM, TGA, DSC, mechanical property test, and contact angle test were conducted to characterize the physiochemical properties of the composites. The results show that there is phase separation at the interface of np-HAp or SA-np-HAp and PLA, and the interface of SC-np-HAp/PLA composite demonstrates strong interface adhesion. Compared with np-HAp/PLA composite, the compressive yield strength and tensile strength of SC-np-HAp/PLA composite increase by 9.4% and 6.6%, respectively, while SA-np-HAp/PLA composite exhibites reductions. Further, compared with np-HAp/PLA composite, the initial decomposition temperature of SC-np-HAp/PLA and SA-np-HAp/PLA composites increases by 7.4% and 5.6%, respectively, and crystallinity of the former increases by 6.7%, while the latter decreases by 3.5%. Compared with np-HAp/PLA and SA-np-HAp/PLA composites, the SC-np-HAp/PLA composite has a significantly lower water contact angle. These results indicate that the SC-modified np-HAp has better interface compatibility with PLA matrix, which will provide a new criterion for the preparation of high-performance bone implant composites.