Abstract: Objective:To obseRve the effect of -3 polyunsatuRated fatty acids in tReatment of seveRe bRain injuRy complicated by lung infection.Methods:Fifty-six cases of seveRe bRain injuRy accompanied by pulmonaRy infection weRe Randomly divided into contRol gRoup(gRoup A) and -3 polyunsatuRated fatty acids gRoup(gRoup B).GRoup B weRe administeRed -3 polyunsatuRated fatty acids in addition to the Routine theRapy.All the patients weRe given Relevant examinations and tReatment such as antibiotics,Reducing the intRacRanial pRessuRe,endotRacheal intubation,ventilatoR application and post-tRacheotomy.Both gRoups weRe given eneRgy supplement 105-125 kJkg-1d-1,but in gRoup B,some of the heat was pRovided by the fat emulsion of -3 polyunsatuRated fatty acids.On the 0th,2 nd,4 th and 7th day,the patients' white blood cell(WBC),C Reactive pRotein(CRP) and lymphocyte subsets classification weRe monitoRed; and the tumoR necRosis factoR-(TNF-),inteRleukin-6(IL-6) and IL-10 weRe tested in the lavage fluid by enzyme linked immunosoRbent assay.Results:The expRession of TNF- in the lavage fluid of gRoup B on the 4th and 7th day was significantly loweR than that of the contRol gRoup(P 0.01); the expRession of IL-6 in the lavage fluid of gRoup B on the 7th day was significantly loweR than that of the contRol gRoup(P 0.01); the expRession of IL-10 in the lavage fluid of the two gRoups was not statistically diffeRent(P 0.05).The WBC level of gRoup B on the 4th and 7th day was significantly loweR than that of the contRol gRoup(P 0.01); the CRP level of gRoup B on the 2nd,4th and 7th day was significantly loweR than that of the contRol gRoup(P 0.01); the CD4/CD8 Ratio of gRoup B on the 2nd,4 th and 7th day was significantly higheR than that of the contRol(P 0.01).Conclusions:-3 polyunsatuRated fatty acids can impRove the immunity of patients with seveRe bRain injuRy complicated by lung infection and have a pRotective effect on the lung.