Based on series expansion theory, the incident Gaussian beam is expanded with spherical harmonics function in this paper. The beam factor of the Gaussian beam is calculated. According to the theory of acoustic radiation force, analytical expression for acoustic radiation force of spherical particles incident on the Gaussian beam is deduced. We valid the method by computing the acoustic radiation force of rigid and fluid spherical particles for different beam waist when the position of the spherical particle deviation from the Gaussian beam center. Simulation results show that the beam width has effect on the acoustic radiation function. When ka is fixed, the acoustic radiation force gradually decreases as the beam width increases. When the radius of spherical particles are relatively smaller than wavelengths, and the spherical particles offset the center of the Gaussian beam equidistantly in the opposite direction, the value of the acoustic force is equal and the direction is opposite.