Abstract: “An Inventory Measuring Attrition Sequence of Relative Clauses” was employed,by recruiting investigate 175 Chinese college graduates, to explore the attrition rules of relative clauses by comparing with acquisition sequence from the previous studies. The following conclusions were derived: (1) Both L1 and L2 learners of different mother tongues share a similar acquisition sequence of relative clauses, that is, the relative clauses of Object(antecedent) Subject(relative pronoun) are acquired first, followed by those of Object(antecedent) Object(relative pronoun) and Subject(antecedent) Subject(relative pronoun).The last acquired are those of Subject(antecedent) Object(relative pronoun). (2) The attrition sequence of English as a second language mirrors their acquisition sequence, and this discovery agrees with Jakobson's Regression Hypothesis,that is, first acquired, last attrited.