A new type of humidity sensor based on optical fiber SPR sensor probe was introduced and manufactured. Firstly the sensitivity of optical fiber SPR sensor probe to environment humidity was studied. On this basis, coating with thin PVA film of different thickness and with capacity of adsorbing water molecule on the surface of optical fiber SPR sensor probe, for the purpose of monitoring relative humidity was proposed. The research shows that the SPR sensor probe coated with double layers of thin PVA film gets better detection result, and humidity measurement sensitivity is 1.59%/%RH, being improved notably compared with SPR optical fiber probe. The SPR sensor coated with single layer of thin PVA film has relative humidity measuring sensitivity of 2.411 nm/%RH related to resonance wavelength in high humidity area. In addition, the new type of optical fiber humidity-sensitive probe with PVA film losing efficiency can be reusable after special treatment.