Blood flow oscillations of 0.001–0.2 Hz are called vasomotion whose physiological mechanism has not been understood. This vasomotion can mirror human body conditions and initiate the pathogenesis sequence in some diseases. In the preliminary measurement of blood flow oscillations in radial artery at the wrist, a strong power spectral density (PSD) at ∼0.1 Hz was found, indicating that low frequency flow oscillations play a dominate role in radial pulse pattern. To understand the interaction between vasomotion and cardiac rhythm in radial artery, numerical simulations were carried out. It is found that the natural frequency of the system decreases with the complexity of microvasculature system, and the inlet oscillating velocity interacts with the natural frequency to generate subharmonics. As the natural frequency in the constructed vessel system can be as low as 0.37 Hz, we speculate that the natural frequency of actual microcirculation is much lower, and the mechanism of vasomotion is actually due to the interaction of cardiac rhythm and microvasculature natural frequency.