Disclosed are a laser radar system and a method for acquiring an image of a target, and the laser radar system includes: a beam source to emit the laser beam; a beam deflector disposed between the beam source and the target, and configured to deflect the laser beam emitted from the beam source in a scanning direction of the target as time elapses; and an optical detector configured to detect the laser beam reflected from the target, which is provided a plurality of beam spots having a diameter DRBS; and a receiving optical system disposed between the target and the optical detector and configured to converge the laser beam reflected from the target, and the optical detector includes a detecting area having a diameter DDA that satisfies an equation of √{square root over (2)}×PRBS+2×DRBS≦DDA≦2×Dlens and an equation of (4/π)×λ×F_number