In supporting semantic Web, knowledge graphs have played a vital role in many areas such as knowledge QA and semantic search. Therefore, they have become a hot topic in the field of research and engineering. However, it is often costly to build a large-scale knowledge graph with high accuracy. How to balance the accuracy and efficiency, and quickly build a high-quality domain knowledge graph, is a big challenge in the field of knowledge engineering. This paper engages a systematic study on the construction of domain knowledge graphs, and puts forward an accurate and efficient method of constructing domain knowledge graphs as "four-steps". This method has been applied to the construction of knowledge graphs of nine subjects in the k12 education of China, and the nine subject knowledge graphs have been developed with high accuracy, which demonstrates that the new method is effective. For example, the geographical knowledge graph, which is constructed using the "four-steps" method, has 670 thousand instances and 14.21 million triples. And as part of it, the annotation data's knowledge coverage and knowledge accuracy are both above 99%.