A facile approach for extracting cellulose nanospheres (SCNCs) was presented through hydrochloric acid hydrolysis of lyocell fibers under hydrothermal condition. The SCNCs showed spherical nanoparticles with an average diameter of 25 nm. Compared to the lyocell fibers, high yield of up to 85.3%, crystallinity of 85.2% and the maximum degradation temperature (T-max) of 347.2 degrees C for the SCNCs were achieved. Moreover, the morphology, microstructure, and thermal stability of SCNCs and rod-like cellulose nanocrystals (RCNCs) were compared. It was found that the SCNCs was less thermally stable than RCNCs, whereas the better suspension stability of SCNCs was observed due to the particular nanospherical structure and the existence of ammonium groups on the SCNCs, and these ammonium groups could easily be removed through heat treatment.