In this paper, we put forward the quasi-hormone model on laser biostimulation (QHML) and the quasi-peptide-hormone model on laser biostimulation (QPHML). QHML supposes the chromophore absorption in a cell allows the photon of low- energy laser irradiation to act as a carrier of bio- information as a hormone does. QPHML further supposes the chromophore absorption in the cell membrane couples with intracellular messenger through GTP-binding protein and mediates laser biostimulation as following: Hot color laser irradiation activates cAMP phosphodiesterase through Gi protein or activates phosphoinositide phospholipase C through Gq protein: cAMP$ARDN, cGMP $ARUP. COld-color laser irradiation activates adenylate cyclase through Gs protein; cAMP$ARUP, cGMP$ARDN. QPHML is verified by its successful applications at the cellular level, the clinic level, and the epidemiological level. In this paper, we also study light-cell interaction from time viewpoint. We define a time representing a process, and show the time parallel principle representing the time relationship of two weakly coupled processes. We then apply the time parallel principle to studying light-cell interaction mediated by the chromophore in the membrane, respectively, and provide theoretical foundation for QPHML.