Facing integration and intelligence requirements of the contemporary magnetic field sensing, a highly sensitive compact magnetic field sensor based on magnetofluid-infiltrated dual-core photonic crystal fiber with gold layer is proposed and analyzed. The mature finite element method is employed to implement optical property investigation. The simulation results demonstrate that when the large hole diameter d1 is 1.80 μm, the small hole diameter d2 is 1.20 μm, the lattice constant Λ is 2.00 μm, the major axis length of the elliptical holes a is 1.875 μm, the minor axis length of the elliptical holes b is 0.75 μm, and gold layer thickness t is 50 nm; the sensor operates near 1.55 μm and the optimal sensing performance can be achieved. Within the detected magnetic field range of 43.00 to 522.60 Oe, this sensor possesses a minimum length of 0.872 mm, a maximum sensitivity of 0.149 nm/Oe with the corresponding magnetic field resolution of 0.0067 Oe and a high linearity of 0.9994. What’s more, the fabrication scheme is also discussed. It is believed that the proposed sensor includes multiple advantages of compactness, high-sensitivity, high-linearity, and ease of manufacture, making it an ideal candidate for magnetic field detection in power systems, oilfield exploration, and aerospace.