The invention discloses a method for monitoring curing degrees in an online manner by the aid of real-time separation on the basis of refractive indexes. The method includes monitoring the refractiveindexes of composite materials in curing procedures by the aid of optical fiber sensors; separating influence of curing of the composite materials and influence of temperature change on the refractiveindexes from each other in real time so as to monitor microwave curing processes of the composite materials in real time. The method has the advantages that the curing processes of the composite materials are monitored in real time, and accordingly the method has important significance in improving the forming quality of the composite materials, shortening the forming cycles and reducing production energy consumption; the difficult problem of incapability of monitoring curing processes of existing composite materials in real time in the prior art can be solved by the aid of the method, and the method has a broad market value and a broad application prospect in the field of technologies for measuring refractive indexes, monitoring curing of composite materials and the like.