A multiplex localized surface plasmon resonance (LSPR) temperature sensor based on grapefruit fiber filled with a silver nanoshell (SNS) and liquid is designed and characterized by the finite element method. Due to the plasmon hybridization in SNS, the designed sensor supports two separate intense LSPR bands that can realize dual-channel temperature sensing at the same time by altering the light wavelength. When temperature increases from 20°C to 80°C, two LSPR bands shift to the shorter wavelength in good linear relationships with wavelength sensitivities of −1.14 and −0.86  nm  /    °  C. The maximum amplitude sensitivity can reach 0.77  °  C^−  1 for peak I with the resolution of 0.01°C. Moreover, the full width half maximum of peak I is <5  nm, exhibiting much better figure of merit than other works, which can provide a new way for multiplex temperature sensing of fiber sensors.