Abstract: Based on the basis theory of three points compacted method, the compaction degree accessing method was proposed in this paper. In this method, the real compaction degrees with various error combinations were got by considering the error between initial water content of compaction samples and water content on rolling field. Then we can get the span of real compaction degree, the probability of real compaction degree bigger than a certain critical value or design index, the probability of approximate compaction degree bigger or smaller than real compaction degree. Based on this method, we can obtain more elaborate information of compaction degree. Therefore, it is better to evaluation the construction quality.