We proposed a closed-form all-in-fiber SCHF-SPR sensor. Using the dual-core directional microstructure for reference, we add a metal layer in the left core to directly enhance the overlapping area of the core mode and plasmonic mode. A theoretical analysis is carried out to simulate the resonant wavelength shift corresponding to RI. An average sensitivity of 2390.91nm/RIU in the RI range 1.33-1.43, and 9294.55nm/RIU in 1.44-1.54 with high linearity and sensitivity is achieved. This SCHF-SPR sensor has a good sensing performance on RI among the existing RI sensors.