QVT (Query/View/Transformation) Relations cannot describe the pattern that includes other patterns, so it has some difficulties in defining the rules of a process model transformation. To solve this problem, the paper extends QVT Relations with three new concepts: Pattern Factor, Nested Relation Expression, and Relationship End Constraint. The paper also discusses the pattern matching and the model creating semantics after the extension. At Last, a case study is presented to show how the extension could deal with process model transformations.