Longjing31 bred by rice research institute of Heilongjiang academy of agricultural sciences is new super japonica variety in cold region. It has many characteristics such as early maturity, high yield, quality, disease resistance and cold-resistant. In this paper, the ancestors were traced and the family tree was constructed. The main characteristics of the parents and the nuclear genetic contribution rate were analyzed in order to expound the genetic evolution process, and it will provide reference for the selection and utilization of breeding parents. The result showed that Longjing31 belonged to Xiabei cytoplasm family, transfer process was Xiabei→Zaofeng→Hejiang20→Hejiang21→Longjing No.10→Longjing13→Longjing31. Nuclear genes were provided by the ancestors at different proportions, including Xiabei, Shishoubaimao, Nonglin11, Xiayi, Tijin, Hongxing No.2, Aoyu239, Quxi17, Tengxi117, Xueguang, Yueguang, Shou921, Kongzhi, Beiming, Kongyu125, Beihai84, Taizhong27, Gaoxiong53, Hexuan58 and Sejiangke. Nuclear genetic contribution rate respectively was 4.6875%, 0.9766%, 2.5391%, 8.2031%, 3.9063%, 3.1250%, 3.9063%, 7.8125%, 15.6250%, 1.5625%, 1.5625%, 3.1250%, 6.2500%, 12.5000%, 0.7813%, 0.7813%, 0.7813%, 6.2500% and 3.1250%. In the parent selection, the adaptability of female parent in the locality should be attended, and the male parent should have the geographical and ecological distant genes. Narrow genetic basis was mainly factors which limit the new breakthroughs of rice breeding in cold region.