The magnetic field sensor based on Photonic Crystal Fiber (PCF) is proposed by tuning the structure and magnetic fluid which is injected into the core. The sensitivity and resolution response of the magnetic field sensor under different magnetic field strength has been calculated for the magnetic field strength range from 100 Oe to 160 Oe. The investigated result shows the highest sensitivity response of 5000 pm/Oe and resolution of 11.33 Oe. The proposed structure has a vital role on nanofluidic technology. Because of the tenability of external magnetic field strength, high sensitivity and resolution the structure gives an awaited technology for the nanofluidics research.