The measurement of seawater temperature in marine environment detection requires large-range and high-resolution. To achieve this objective, a reflective-type optical fiber sensor based on the cascaded no-core fiber ( NCF) and fiber Bragg grating ( FBG) is proposed, which is also evaluated. The manufacturing process of the sensor includes three steps. First, the coated-NCF is fused to the single-mode fiber (SMF) inscribed with FBG. Then, the gold film is plated on the other side of the NCF to form a reflector. Finally, the fiber structure is encapsulated in the capillary. It is worth noting that the NCF without coating is a multi-mode waveguide, while the NCF with coating can be regarded as an anti-resonant reflecting optical waveguide. Theoretical analysis shows that the output spectrum is achieved by the superposition of multi-mode interference and anti-resonance effect. Due to the high thermal optical coefficient of NCF polymer coating, the position of the interference wavelength in the spectrum shifts obviously with the temperature change. According to the position of the FBG center wavelength and the interference wavelength, the accurate temperature value can be calculated through the corresponding fitting curves. Experimental results show that the minimum detectable temperature resolution is 0. 000 1℃ in the range of -6℃ ~ 54℃ . This reflective sensor has advantages of convenient processing, compact structure, and high sensitivity, which has great potential for large-range and high-resolution seawater temperature measurement applications.