Global warming during the 20th century,especially the impacts of the global warming in the past two decades,has been paid much attention worldwide.A case study is made in this paper on the relationship between change of main grain crops structure and global warming in Heilongjiang Province,Northeast China,based on the statistical data of agriculture and ground based climate data during 1980 to 2000.Wheat,corn and rice are the three main crops planted in this province,the varieties of which indicate the human's response to the climate change.K-Means analysis is employed in this paper.It is found that,with the climate warming,the seeded area of rice has increased from 2×105hm² to 16.06×105hm²,that of wheat deduced from 20.379×105hm² to 5.9×105hm²,and the area of corn has been escalating.Thus the planting structure has been changed from wheat and corn in domination to corn and rice in domination in the past 20 years.The relationship between the main crops structure and the global warming is very evident.The northern planting boundary of the rice in Heilongjiang Province has extended to 52°N at north,and been pushing towards the east.The borderline of corn advanced to the north.At the meantime,the seeded area of wheat retreated northward.Changes of the main grain crops structure lie on the warming up procedure in Heilongjiang Province under global warming,which proved that temperature change has influenced human society to a certain extent,and people began to adapt to the new environment by transferring the land use patterns.