Abstract: Based on the reliability theory, this paper presents the concept of unblocked reliability to evaluate highway network performance. Aimed at the problem of too many optional schemes in the road network plan, the node connective importance and road unit importance are analyzed to decrease the number of optional layout scheme and road degree schemes. Using the integrated benefit of the road system as optimization objective, the optimum model of highway network planning is built. Through the enumeration method, the optimum plan can be found. Then, an example is given to illuminate the practicability and maneuverability of the optimum model and solution for highway network planning.