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　the　road　unit　importance　are　analyzed　to　decrease　the　number　of　optional　layout　schemes　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.