The relationship between boresight error and returning signal from the illuminated target is studied theoretically. The operating principle of a new-style adaptive-optics device, which is named adaptive fiber-optics collimator with the abilities to correct both laser beam transmission error and pointing error, is introduced. The laser beam pointing experimental setup with a laser propagation distance of 200 m through horizontal atmosphere is established. Based on returning signals from the illuminated two-dimensional and three-dimensional targets, the beam pointing closed loop using stochastic parallel gradient descent algorithm (SPGD) algorithm is achieved under different initial boresight errors. The experimental results indicate that the evaluation parameters of the residual boresight errors are less than 6% and 10.8% for the two-dimensional target and three-dimensional target, respectively, which are within the tolerance of theoretical analysis. Finally, the influence of SPGD parameter on moving-target pointing is analyzed.