Numerous researches have already revealed the existence of sheepskin effects and proved the signaling value of education based on empirical materials from developing or developed countries; however, only a few empirical studies have explored the mechanism lying behind the proved educational signaling value. With this regard, based on recent 6-year cross-section data from China General Social Survey, the authors discussed the interactive effects between the educational signaling value and parents' educational level. After correcting the selective bias and endogenous issues by multiple methods--Heckman two-stage, IV, and comprehensive models combined HTS and IV--it finds that there exist obvious sheepskin effects in the returns to education in China and robust complementary effects between parents' educational level and the signaling function of individual's education on their personal income.