To adapt to compact space requirements of high power laser system, a far-field and near-field coupling scheme based on second order ghost image is used in high power laser collimation technology. A sensitive small-size collimation optical system is designed and built. We present complete test scheme and verify its feasibility. The near-field measurement sensitivity is 7.04 μm/pixel and the far-field measurement sensitivity is about 18.14 (″)/pixel. The influence of far-field change on near-field is researched and used to optimize beam collimation. Compared with traditional collimation system of far- and near-field separation, this scheme sharply reduces the number of light paths and devices under the condition of imaging quality and resolution assured. It is more convenient to feedback the interaction effect and collimation of far-field and near-field.