In this work, an enhanced photonic crystal fiber based on Surface Plasmon Resonance sensor using a sided polished structure for detection of toxic ions arsenic in water is presented. The SPR curve can be obtained by polishing the side of the PCF after coating the Au film on the side of the polished area, the SPR curve can be obtained. The proposed sensor has a clear SPR effect, according to the findings of the experiments. The calculated the Signal to Noise Ratio (SNR), Sensitivity, Resolution and Figures of Merit (FOM) are approaching, SNR is 0.0125, S 11.11 𝜇m/RIU, the Resolution is 1.8x10−4 and FOM is13.88 is a chivied, While the effective performance parameters for MMF-PCF-MMF such as the sensitivity is approaching 2.5 𝜇m/RIU, SNR is 0.0173, FOM is10.86 and the Resolution is 4x10−4 is a chivied. The proposed sensor is possesses a good mechanical strength, low cost, and an easy fabrication ,allowing it to provide a greater measurement range and action area to the measured samples without lengthening the sensor.