A kind of magnetic field sensing structure based on magnetic-fluid-clad no-core single-mode no-core fiber was proposed and designed. The no-core fiber in this structure can excite cladding mode and combine the core and cladding modes of the intermediate sensing single-mode fiber. The transmission spectra of the as-fabricated sensing structures at different external magnetic field strengths and ambient temperatures were investigated experimentally. The corresponding magnetic field sensing properties and influence of ambient temperature were obtained. Experimental results indicate that the valley wavelengths at around 1 462 nm and 1 477 nm shift to long wavelength side with the increase of external magnetic field. The achieved sensitives are 67.28 pm/Oe and 49.82 pm/Oe, respectively. The valley wavelength at around 1 462 nm shifts to short wavelength side with the temperature increase and the corresponding sensitivity is 37.8 pm/℃. The proposed sensing structure possesses the advantages of easiness of fabrication and high sensitivity, which is promising for future pragmatic applications.