The representational levels of students with different abundance of disciplinary domain knowledge were investigated in 5 categories arithmetic equations by a "study-test" pattern. 62 subjects attended the experiment. The results showed: “S+P+” equations led a significant effect on false memory but equations with surface feature’ absence led the false rate significantly reduced in two groups. Moreover, no matter principled features were present or not, the reaction time on equations with accordant surface features did not have significant differences between two groups, but on the correct recognition rate, rich group was significantly higher. The results indicated, both poor and rich groups encode surface and principled features in the same serial processing, with surface features preceding principled. The extraction clew of poor group based on surface features; principle features were discarded because of its interference. The process of surface features by rich group required additional cognitive resources but there was no interference in principled features processing. Both surface and principled features were considered as extraction clew.