This study designs and fabricates a dual-parameter measurement sensor based on a multi-mode thin-core multi-mode fiber structure. Mach-Zehnder interference (MZI) and surface plasmon resonance (SPR) are simultaneously generated in this structure to measure the refractive index and temperature. Two multi-mode fibers (MMFs) are used as the input and output couplers, and the thin-core fiber (TCF) is coated with a metallic silver film as the sensing arm. The refractive index sensitivity of MZI and SPR is $-$70.373 nm/RIU and 4888.77 nm/RIU in the range of 1.333?1.412 RIU, and the temperature sensitivity is 73.48 pm/℃ and $-$0.3215 nm/℃ in the range of 20?80 ℃, respectively. The sensitivity matrix is used to realize the two-parameter measurement, resolving the cross-sensitivity of the temperature of the refractive index sensor. The sensor is characterized by low cost, high sensitivity, and simple fabrication. Moreover, it has good application prospects in biochemical medical detection.