After changes are made to a previously tested program, a goal of regression testing is to retest the program based only on the modification while maintaining the same testing coverage as the complete retesting of the program. Several regression techniques for structural programs using data flow or partial data flow (also known as program slicing) have been proposed. With the object oriented (OO for short) method growing mature, there is an urgent need of testing techniques for OO programs. In this paper, based on the analysis of characteristics of OO system, firstly, the dependency relations among objects are defined, from which series of objects' methods are deduced. Secondly, program slicing techniques are used to identify test cases to be applied to modification. Finally, a complete regression approach to OO program is presented.