4H-SiC metal-oxide-semiconductor (MOS)-based devices appear to worse electrical performance when exposed to electron irradiation, owing to the production of material defects. This study demonstrates an analysis of defect evolution of 4H-SiC MOS capacitors with the simplest structure, subjected to a series dose of electron irradiation with 10 MeV electron beam, including 30, 50, 100, 500, 1 000 kGy. Deep level transient spectroscopy (DLTS) test and capacitance-voltage (C-V) measurement were used to obtain defects information among MOS samples pre- and post-irradiation. DLTS results present that a low dose of irradiation causes no evident impact on defect evolution near and at the 4H-SiC/SiO2 interface, whereas a high dose of irradiation makes a defect configuration of carbon interstitial dimer defect evolve into another more stable one at a deeper energy level. C-V curves show that different irradiation doses lead to different negative shift degrees of flat-band voltage. This is considered to be resulted from multiple factors, including oxygen vacancies in the SiO2 layer and defects near and at the 4H-SiC/SiO2 interface. This work might be helpful for the development and optimization of 4H-SiC MOS fabrication with respect to anti-irradiation performance.