Objective：To compare the marginal microleakage and hardness between the SonicFill bulk filling resin and the conventional resin，layer and holistic filling in the cavity of the tooth fossa. Methods：Class Ⅱ cavities were respectively prepared on mesial and distal surfaces of forty molars，rinsing and etching enamel，coated with acid etching binger，and illuminated for 20 seconds. The teeth were randomly divided into two groups，in group A，the cavity on one side was filled with SonicFill bulk filling resin，each layer of 2 mm（A1）；the cavity on the other side was filled wity Neofil filling resin，each layer of 2 mm（A2）；in group B，the cavity on one side was filled by SonicFill bulk filling resin integrally（B1），the cavity on the other side was filled by Neofil filling resin integrally（B2）. The Vickers microhardness of the filling materials was detected. Samples were immersed in a 2% methylene blue solution at 37 ℃ for 24 hours，and cut along axis twice，the thickness of slice was about 1 mm，dye leakage was observed under a stereo microscope. Results：There were statistically significant differences in the Vickers hardness and their ratio among different groups，the order was as follow：B1>A1>A2>B2. The marginal microleakages of group A2 and B2 were significantly higher than those of A1 and B1 group，and the difference was statistically significant（P < 0.05）. Conclusion：Compared with Neofil resin，the overall and layered filling of SonicFill bulk resin filling materials have better edge tightness and hardness.