Abstract: The general geometric constraint graph based on assembly features presents a clear model for solving geometric constraint satisfaction problems and avoids the shortcomings of hypergraph and fuzzy characteristics commonly met in the ordinary geometric constraint graph.It is used to analyze the cause of constraint collision.This approach of space analysis defines and deduces the spaces and conditions of constraint satisfaction,and presents the method to calculate DOF and freedom space.It can detect constraint collision and its causes of occurence in the incremental evaluation of geometric constraints.