Abstract: Motion of microscopic particles has been a very interesting topic.In order to explain the matter wave diffraction problem better,this paper using the new method of quantum theory to studies the Double-slit diffraction of C₆₀ molecules using the new method of quantum theory.First,solve the Double-slit diffraction of C₆₀ molecules wave functions by Schrodinger equation.Then calculate the diffraction wave function after the slit of C₆₀ molecules with the Feynman path integral quantum theory.To obtain diffraction wave function of diffraction screen.Finally the analytic relation between the double-slit relative diffraction intensity and diffraction pattern position of C₆₀ molecules is obtained.The calculation results are in good agreement with the experimental data.This shows that the diffraction microscopic particles need to be studied with quantum theory method completely.This method has universality for the study of the motion of microscopic particles.It also can be used in the study of single slit diffraction,Multi-slit diffraction and grating diffraction for matter wave and other particles.

Key words: double-slit diffraction, quantum theory, decoherence effects