The preparation of chitosan-coated magnetic nanoparticles (MNPs) and covalent immobilization of alpha-amylase for starch hydrolysis was investigated. Surface morphology, chemical composition, and structural characteristics of the MNPs were analyzed by scanning electron microscopy, energy dispersion spectrometry, and X-ray diffractometry, respectively. Surface functional groups of MNPs, chitosan-coated MNPs, and alpha-amylase-immobilized MNPs were characterized by Fourier transform infrared spectroscopy. Response surface methodology based on three levels was implemented to optimize three immobilization conditions and a regression model was developed. alpha-Amylase-immobilized MNPs provided better stability towards pH and temperature. The prepared thermostable nanobiocatalyst is well-suited for industrial processes involving starch hydrolysis.