Soliton model is suggested to explain the main properties of the delayed luminescence spectra of simple biological systems. Solitons describe self-trapped localised electron or exciton states in low-dimensional biological macromolecules, like alpha-helical proteins, actin filaments, microtubules, etc., and provide charge and energy transport on macroscopic distances in main biological processes. Such a model explains the long duration of the delayed luminescence of bio-systems, its kinetics and dependence on the intensity of the stimulating light.