Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS). Results show a high branching degree of PLA (similar to 49.5%) can be effectively obtained with adding only 1 wt % PETA, contributing remarkably to enhancing strain hardening. The density of the nuclei formed during nonisothermal crystallization for LCB-PLA samples is markedly increased contrasted with PLA, resulting in significantly enhancing crystallinity from 13.3% to 41%, the onset crystallization temperature (similar to 20 degrees C), and the crystallization rate. Interestingly, compared with mini-injection molding, the elevated wall shear rates (and corresponding shear stresses) prove to be beneficial to the creation of special crystalline morphologies (beta-crystal form) and oriented structures under microinjection molding conditions, resulting in the improvement of tensile strength by similar to 45 MPa.