The invention discloses a method for detecting an object to be detected by using an SPR biosensor. The method uses a biotin-streptavidin-magnetic particle as a signal reporting molecule which can amplify a signal of a hybridization result; therefore, the problem that marking of a probe or an object to be detected before hybridization influences natural binding of biological molecules is avoided, the requirement of improving detection sensitivity of the SPR biosensor is realized, and generated signals are stable and are easy to detect, which enables result detection and analysis to be substantially simplified. According to the invention, amplification of a detection signal is realized after hybridization, so variation and variation quantity of SPR signals before and after the detection signal is amplified can be more visually and clearly observed; meanwhile, the biotin-streptavidin-magnetic particle technology is used in the invention, and no expensive detector is needed, thereby reducing technical cost and economic cost needed for enhancing sensitivity of the biosensor.