[Objective]The prevalence and transmission of swine influenza in Shaanxi Province were studied.[Method]Nasal/tracheal swap samples were randomly collected from apparently healthy pigs in farms and slaughterhouses in Shaanxi province between October 2011 and May 2012. The samples were firstly separated by SPF chick embryos, and the HA-positive samples were identified as swine influenza virus using RT-PCR. Then, the full genomes of these isolates were sequenced and used to re-construct phylogenetic trees with software MEGA 4 and analyze genetic variations. [Result] Six H1N1 influenza viruses were isolated and identified among 500 samples, with isolation rate of 1.2%. The full length genomes were obtained from six isolates, with nucleotide similarity of 98.3-99.1% . Phylogenetic analysis showed that six H1N1 virus isolates were located into the lineage of avain-like H1N1 swine influenza viruses. The nucleotide similarities were 97-99% between six isolates and SIVs from Jiangsu, Liaoning, Shandong, and Hong Kong. The mutated nucleotides of eight gene fragments for six isolates were detected at receptor binding sites and potential glycosylation sites. These genetic variations will affect antigenicity, host adaptability and virulence of the viruses.[Conclusion] The H1N1 swine influenza virus were firstly isolated from apparently healthy pigs in Northwestern China, and six full length genomes of these isolates were obtained. Phylogenetic analysis suggested six isolates were avain-like H1N1 swine influenza virus. Mutations were also detected in some amino acid sites of these isolates.%[目的]监测陕西省猪流感的流行与传播情况，为猪流感研究提供参考。[方法]从生猪养殖场和屠宰场表观健康猪中随机采取猪鼻/气管拭子样本，经SPF鸡胚分离，对HA阳性样本进行猪流感病毒RT-PCR鉴定。测定分离株全基因序列，通过MEGA4构建基因进化树，并进行遗传变异分析。[结果]从500份样本中分离鉴定出6株H1N1流感病毒，病毒分离率为1.2%。获得6个核苷酸相似性为98.3%-99.1%的分离株全基因序列。遗传进化分析表明6个分离株都位于avain-like H1N1猪流感病毒谱系，与中国江苏，辽宁，山东和香港等地H1N1猪流感病毒株同源性达97%-99%。6个分离株的8个基因片段均在蛋白受体结合位点、潜在糖基化位点等处发生核苷酸变异，这将会影响猪流感病毒的抗原特性、宿主适应性和致病力。[结论]首次从西北地区表观健康猪中分离到H1N1猪流感病毒，并获得6个分离株的全基因序列。遗传进化分析表明，6个分离株为avain-like H1N1猪流感病毒,且多处氨基酸位点发生变异。
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