A novel emitting system of fiber-array 3D laser imaging using off-axis three-mirror system was proposed. High-power laser was split to certain number of beams by fiber splitting and output with fiber-array. The off-axis three-mirror was designed as normal telescope system, and its focus length was the divergence angle divided by the core diameter of the fiber, while the F number in image space was determined by the Numerical Aperture(NA) of the fiber. The total field of view was the focus length divided by the length of the fiber-array. The fiber-array was set on the focus plane of the off-axis three- mirror system, and rays were traced in the opposite way of design. The example system realized divergence angle as 20 μrad of 51 fiber beams, and it showed that the divergence angle of every fiber beam satisfied the target value well and the footprint between the neighbouring beams has good uniformity on the target surface. Besides, this emitting system was suitable for any number of laser beams within the total design field of view.