Developing materials from renewable resources to produce nanocomposites with satisfactory mechanical properties is a vital progress in today's society, and meanwhile, the widespread use of these nanocomposites needs to be enabled through large-scale manufacturing. Herein, ultra-strong nanocomposites with an aligned structure that consisted of bio-based, biodegradable poly(lactic acid) (PLA) and cellulose nanocrystals are demonstrated, and these nanocomposites can be manufactured at a large scale through surface modification of the nanocrystals, liquid-assisted extrusion, and solid-state drawing. An ultimate strength of 353 MPa and a toughness of 107 MJ/m3 can be achieved by these nanocomposites, which are superior compared to the values of many other thermoplastic materials. The mechanism that explains the high toughness of these nanocomposites has been extensively investigated, revealing that sliding of the PLA crystallites present in the materials is the main factor. Moreover, these nanocomposites possess relatively high glass transition temperature and exhibit strain-responsive birefringence behavior, which indicates their great potential in not only structural applications, but also optical strain sensing areas.