Multimode fiber interference based on no-core fiber (NCF) is very sensitive to the refractive index variation of its external medium.The transmission characteristics of multimode fiber interference based o n no-core fiber are theoretically analyzed in detail,and the solution concentration sensing charact eristics are experimentally investigated.The multimode interference in expe riment uses a segment of no-core fiber with is 4.4mm in length and 104μm in diameter,the transmission spec tra of which are quite distinct and recognizable,and the depth for a single peak is more than 20dB.Th e theoretical transmission spectrum shows a good agreement with the experimental one,and it indicates that the taper between single mode fibers and no-core fiber in the multimode interferenc e used in experiment has little influence on transmission spectrum of the multimode interferenc e.The wavelength of peak in its transmission spectrum shifts 26.5nm when the c oncentration of glycerol s olution varies from 7wt% to 70wt%,and a good agreement in cubic functi on with the variation of the solution′s concentration is presented.The investigation shows that the interference based o n no-core fiber responds to the change of solution concentration around the no-core fiber continuous ly,instantly,and significantly.