Using the semi-classical theory, density matrix method and probe-field approximation and taking into account the relaxation effect, we have investigate the Stark split phenomenon for a two-level system interacting with a strong resonant biohromatic field. In the case of two strong fields having same amplitude and symmetrical detuning of frequency, the relaxation effect not only influences the weight of splitted levels created from the optical Stark effect and broadens these levels, but new splitted levels can be found in a new position. It is predicted that new satellito lines of spectra can be observed in optical spectrum. These results, differ considerably from, that in the case of mono-ohromatio field and provious work on the biohromatic field withou.t taking into oonsideration of the relaxation. In the oasis of mono-chromatic the effecl) of relaxation only influenoes the weight and width of Stark splitted levels but 110 new splitted levels can be found. Because the relaxation effeeii produced by spontaneous emission between upper and lower levels in real atom and molecule system, usually cannot be neglected, the results of thia paper can be used in piaotioal applications.