Abstract: In the classic diffusion theory, the diffusion of molecules and objects is isotropic,since they are usually assumed as spheres. When we see those molecules and objects down to nano-scale, most of them exhibits various asymmetrical structures instead of spheres. Correspondingly,the diffusion of these molecules and bjects displays orientation-dependent behaviour when the observation time is less than dozens of nanoseconds. Take methanol for instance, the drift of diffusion is about 10% of the total diffusion within a finite time interval of 100 ps. This observation of asymmetrical diffusion within finite time scales extends the theory of molecular diffusion and is of great importance to the understanding of life and nature phenomenon. Such asymmetrical diffusion also suggests a method for driving molecules by controlling their orientations.