A model was developed for the interactions between glycogen and biomacromolecules by gold nanoparticle plasmon resonance light-scattering method. The interactions between glycogen and biomacromolecules can alter the aggregation status of gold nanoparticles, which produced intensity changes in plasmon resonance light-scattering. This is a sensitive method to study the interactions between glycogen and biomacromolecules from nano- to micromolar level. And it is also a simple method that measurement can be carried out with a common fluorospectrometer using label-free gold nanoparticles as the transducer.