In this microarticle, we design a microstructure photonic crystal fiber (PCF) based external sensing surface plasmon resonance (SPR) sensor. The performance of the design is numerically evaluated incorporating the finite element method (FEM) with Perfectly Matched Layer (PML) boundary condition of scattering case. Modal analysis is performed using finer mesh anlaysis. At the optimized thickness (40nm) of chemically stable gold(Au) layer, the ever been maximum reported wavelength sensitivity (WS) and standard amplitude sensitivity (AS) are to 75,000 nm per RIU and 480 per RIU correspondingly. The sensor also exposed high polynomial fit (𝐑𝟐 = 𝟎. 𝟗𝟗) as well as high figure of merit (FoM) of 280.77 per RIU. Since very much high sensitivity, high detecting range and figure of merit, lowing the cost of fabrication, the proposed design can be a pleasant competitor in detection of the analyte refractive index (RI). At the last, to prove performance ability of our designed sensor all the performance parameter calculated results compare with the existing sensors.