The utilization of building energy consumption data is still inefficient. According to this problem, in this paper, a new method based on Hadoop for data mining of public buildings energy consumption combining with building information is proposed. The paper designs the data mining system of public building energy consumption based on Hadoop, and performs designs and illustrations to the basic framework and functional modules. Apriori algorithm and C4.5 algorithm are implemented distributively using MapReduce programming model. The paper takes 100 office buildings in Shandong Province as examples to analyse the data of air conditioning system energy consumption. The experimental conclusions are the influence rules of 6 kinds of building information on air conditioning system energy consumption. Moreover, the experiment obtains the decision tree of air conditioning system energy consumption. According to the decision tree, we can distinguish the energy consumption level of air conditioning system, and offer targeted advice on energy saving renovation of sample buildings.