With the development of urbanization in northwest region, the high loess-filled project has become an important research topic. In this paper, indoor standard compaction tests are carried out to research theoretical problems, influencing factors，and numerical solutions. The results show that：(1) According to the energy conservation theory, it finds that the calculated unit volume compaction standard values given by different industry geotechnical testing rules are a little smaller than loess in Yan'an region. (2) By introducing the concept of air content, this paper finds that the compacted Q3 loess sample is higher in air content than the compacted Q2 loess sample. (3) By defining the concept of obtainable compaction coefficient and structuring relation curve of obtainable compaction coefficient and saturation level curve, this paper finds out that in specific conditions of the dry density, select the value of the left side of optimum water content is more appropriate. (4)Combining with several main factors can structure the optimal range of water content, and controlling water content in the optimal range rather than the optimum water content value, the use of water can be reduced and the construction quality requirement can be also ensured.