Ultrasound radiation force has been shown promising in facilitating ultrasonic molecular imaging and target drug delivery. A chirp excitation technique is developed to improve the translational displacement of microbubbles in this study. Based on a modified RP equation and a particle trajectory equation, we investigate the dependence of the translation of microbubble clouds on the chirp parameters （center frequency and frequency shift） and bubble radius distribution. Results demonstrate that the chirp excitation performs better than the traditional sinusoidal excitation in displacing widely distributed microbubbles and bubble clouds with radius far from resonant size. For example, for Gaussian size-distributed microbubble clouds with mean radius 3.5 μm and variance of 1, a 1 MHz center frequency chirp with frequency range 0.75 MHz induces about 12% more microbubbles displaced over a distance of 30 μm during 200 μs insonification, compared with a 1 MHz sinusoidal excitation with equal acoustic pressure.