This paper studies a humidity dual biconical fiber sensor coated with agarose gel. The sensor was fabricated by the taper drawing technique of using a LZM-100 fusion splicer from single mode fiber, forming a Mach-Zehnder interferometer. Humidity modifies the refractive index of the coating layer, which in turn alters the high order modes along the dual biconical fiber segment and causes a detectable shift to the interference pattern. Due to the strong light absorption of agarose at 2 μm, the sensitivity of sensor was greatly enhanced. It has been found that the sensor’s sensitivity operated at 2 μm is tens of times higher than that at 1.55 μm region.