Abstract: The theory of enhancement of weak-gain Raman modes of sti mulated Raman scattering (SRS) by dye-lasing gainis established in this paper.With the classical theory of electro magnetic field,the Raman gain gR,dye-las-ing gain gD and total loss α are calculatedin detail andthe expression of each quantityis also presented.In the processof giving out gD,the result of classical theoryis amended.Finally,the explicit expression whichindicates that the SRS intensity is exponentiallyincreased by lasing gain is obtained.Further more the observed experi mental phenomenon is explained well according to this theory.