Abstract: This paper studies the influence of bi-dye on the output of flashlamp-pumped dye laser from the point of donor-acceptor dye system.We consider that radiation energy-transfer is the dominant energy transfer mechanism between donor and acceptor under low concentrations.After calculating the spectrum inversion rate of donor and acceptor,we conclude that in the donor-acceptor system the concentrations of donor and acceptor is low.We point out that separating donor from acceptor is the optimum way to use multi-dye system.Base on the theoretic analysis,we carry out some experiments on the repetition rate flashlamp-pumped dye laser,the results of the experiments agree with those of the theoretic analysis.