目的:对天津市新型冠状病毒肺炎(Coronavirus Disease 2019, COVID-19)国内感染和境外输入确诊病例的上呼吸道标本进行新型冠状病毒(2019 novel coronavirus, 2019-nCoV)全基因组序列测定，并完成基因变异位点和进化分析。方法:对天津市COVID-19国内感染和境外输入确诊病例共24例的上呼吸道标本进行核酸提取，构建DNA测序文库，第二代测序仪上机测序，拼接测序数据，通过基因比对和构建进化树完成病毒基因变异位点和进化分析。结果:24例COVID-19确诊病例上呼吸道样本2019-nCoV测序结果均与参考株Wuhan-Hu-1高度同源，相似度均大于99.9%；6例国内感染病例2019-nCoV为谱系S，其余18例2019-nCoV为谱系L；境外输入病例2019-nCoV有48个突变位点，国内感染病例2019-nCoV有14个突变位点；15例境外输入病例2019-nCoV中发现D614G突变，国内感染病例2019-nCoV均无此突变。结论:天津市COVID-19确诊病例中，境外输入病例病毒基因组有更多的核苷酸变异位点，并且大多数出现D614G突变，传播能力更强。“,”Objective:To collect the upper respiratory tract specimens from both domestically-spread and imported Coronavirus Disease 2019 (COVID-19) confirmed cases, sequence the whole genome of 2019 novel coronavirus (2019-nCoV) and analyze the genetic variation and the phylogenetic characteristics.Methods:The viral nucleic acids of all specimens were extracted, the sequencing library was constructed following the manufacturing instructions, and the sequencing data were analyzed by bioinformatics software.Results:The whole genomes of 2019-nCoV strains from 24 samples were all obtained and had high similarity with the genome of the reference strain Wuhan-Hu-1 (GenBank ID: NC_045512) and the similarity rates were all greater than 99.9%. Six 2019-nCoV strains from domestically-spread cases were classified into L-lineage and the others were S-lineage. The 2019-nCoV strains from the imported cases had 48 nucleotide mutation positions, but those from the domestically-spread cases only had 14 mutation positions. Most of 2019-nCoV strains from the imported cases (15/16) had the specific D614G mutation site in spike protein, while those from the domestically-spread cases had none.Conclusions:The 2019-nCoV strains from the imported cases in Tianjin city had more mutation sites than those from the domestically-spread cases, and most of 2019-nCoV strains from the imported cases had D614G mutations in spike protein which had more transmissive rates and were easier to spread among humans.