The invention discloses a method for testing interface impervious strength of the sample bonded by sealant and concrete. The method comprises: reserving a seam cavity of a certain size in the middle of the concrete bonded sample, filling in sealant to bond the concrete and the sealant into an integral body to obtain a truncated cone shaped bonded impervious sample; placing the bonded impervious sample on the permeability instrument; increasing the water pressure of the impervious instrument at regular intervals for 0.1MPa each time from 0.1MPa until water seeps from the sample surface; and determining the previous water pressure as the impervious strength of the interface of concrete and sealant. The invention achieves the advantages of simple operation, unique and convenient using, need not adding other equipments, is convenient for popularization; it can detect the impervious strength of any composite material structure, has good instructiveness to engineering practice, is especially suitable for detecting the impervious strength of concrete construction seam and expansion joint such as simulated reservoir dam surface, channel expansion joint, aqueduct expansion joint and pipeline expansion joint, achieves great practical engineering value.