Spontaneous photon emission was produced by the transition of the living biological system from upper-state to low-lying state. According to Frhlich’s theory, living biosystem is an extreme coherence’s open system. The motion state possesses a collective vibration effect and the biosystem can be regarded as a set of vibrators with same character. The transmit equation of biophoton in biosystem was deduced. This is a typical Sine-Gordon equation. It showed biophoton has soliton character in the living biological system. In conclusion, biophoton can be an ideal carrier of biosystem information. Furthermore, the interaction of weak laser photon with biomolecule system is discussed in this work. It shows that weak laser irradiation can excite the biologic vibrator from excited state to lower energy state with relaxation phenomenon and photon emission.