Documents are often analyzed based on features.Evaluation of important degrees of features is a basic work of document analysis.Now this work is done mainly by human,so the workload is too large and results are subjective.Three statistical methods are proposed based on the actual usage of features in a large number of documents.The statistical values and those from experts are contrasted and analyzed,and then a selection result based on voting is given.Some results from 500 document samples are given.