Abstract: Directional drilling can provide an advanced method of pipeline installation in pipeline crossing. Compared with conventional methods of pipeline installation, directional drilling has significant advantages of maximum depth pipeline installation, short time limit, without influencing traffic and least environmental pollution. The ZD1 small-sized directional drilling system has been developed by Pipeline Scientific Institute, with crossing length of 150 m, depth of 5 m and pipe of 250 mm in diameter. This system consists of drilling rig, hydraulic system, slurry system, drilling topis and locating & leading system. The DZ1 system has completed two directional holes. Through field test over a month period, the results show that the system fully conforms to the design requirments. The major technological parameters of the system are given in the paper.