The construction of the high-intensity heavy-ion accelerator facility (HIAF) Yang et al. (2013) [1] at the Institute of Modern Physics, Chinese Academy of Science (IMP, CAS), has begun recently in Huizhou, Guangdong province, China. One of the devices of the HIAF is the Spectrometer Ring (SRing). Designed with two magnetic alloy (MA) loaded cavities to decelerate the heavy-ion beams, such as a ²³⁸U${}^{+92}$ beam from 800 to 30 MeV/u, the SRing will serve as a multi-functional experimental storage ring. The MA cavity design works in the frequency range of 1.006-0.503 MHz with a maximum voltage of 50 kV and peak power of 220 kW. This study describes the variable-harmonic RF deceleration cavity design and a performance test of Chinese MA cores.