This paper introduces a method for fiber Bragg grating (FBG) multiplexing based on spatial mode diversity. By introducing the dimension of spatial modes in few-mode fibers (FMF), the FBGs are allocated into multiple optical paths carried by different spatial modes. The method involves multiplexing and detecting the reflected spectra of FBGs in various spatial modes, effectively enhancing the system's sensing capacity. The paper establishes a mode-diversity multiplexing sensing system using mode-selective photonic lanterns and FMF circulator. As a proof of concept, the system is experimentally validated for multipoint temperature sensing using four spatial modes LP01, LP11, LP21 and LP02, and its performance is compared with that of traditional multiplexing methods. The experimental results indicate that the proposed mode division multiplexing (MDM) and hybrid MDM/wavelength division multiplexing (WDM) schemes effectively enhance the sensing capacity. Furthermore, the sensitivity to temperature response for the LP01, LP11, LP21 and LP02 modes in the spatial mode diversity multiplexed sensing surpasses 0.0096 nm/°C, maintaining linearity above 97%, and the maximum error contained within 5%. The proposed method offers a novel approach to expand the capacity of sensor networks.