To explore the bacteriostasis effect of Qiguiyin decoction combined with antibiotics inhibiting multi-drug resistant pseudomonas aeruginosa in vitro. Methods： The antibacterial situation of antibiotics, blank serum, Qiguiyin decoction–containing serum and Qiguiyin decoction & antibiotics-containing serum in vitro were detected with double dilution method. Results： Blank serum had no effect of bacteriostasis on multi-drug resistant PA, while Qiguiyin decoction-containing serum had significant effect of bacteriostasis on it, and there was significant difference between them. Besides, the serum with both Qiguiyin decoction and antibiotics showed more significant bacteriostasis effect. Conclusion： Qiguiyin decoction-containing serum could reduce the content of MIC, MBC in antibiotics and increase the bacteriostasis rate. Qiguiyin Decoction-containing serum and antibiotics have significant cooperation effect of bacteriostasis on PA in vitro.