[Objective] This paper takes a 1.5 kW canned permanent magnet synchronous motor (CPMSM) as the research prototype to reveal the influence laws of can materials on the demagnetization characteristics and electromagnetic performance of CPMSM under three-phase short-circuit fault conditions. [Methods] First, the field-circuit coupling calculation method was adopted to comprehensively compare and analyze the key electromagnetic performance indices of CPMSM with SUS430, SUS316, and SUS304 can materials, including three-phase short-circuit current, permanent magnet demagnetization coefficient, air-gap flux density, induced electromotive force, and output torque. Subsequently, the anti-demagnetization mechanism of the motor was revealed by combining the no-load leakage flux coefficient and the operating point of permanent magnets. Finally, a prototype motor was manufactured, and experimental tests were conducted to verify the accuracy and reliability of the established finite element simulation model. [Results] Under three-phase short-circuit fault conditions, the CPMSM with SUS430 can exhibited significantly lower peak d-axis and q-axis currents and extremely slight demagnetization of permanent magnets. Its air-gap flux density, stator flux density, back electromotive force, and output torque remained basically stable before and after the short-circuit fault, with only a slight increase in torque ripple. In contrast, CPMSMs adopting SUS304 and SUS316 cans suffered severe permanent magnet demagnetization. Specifically, the back electromotive force dropped by more than 64%, the average output torque decreased by 54.6%, and the torque ripple was drastically aggravated after the short-circuit fault. [Conclusion] The magnetic SUS430 can effectively improves the anti-demagnetization capability of the CPMSM during three-phase short-circuit faults. The can permeability is identified as the core parameter dominating the demagnetization characteristics of the CPMSM. The research results of this paper can provide a reliable reference for can material selection and anti-demagnetization design of CPMSMs applied in vacuum pumps and other relevant fields.