THE SUBWAY-NETWORK IN TOKYO HAS SPREAD ITS OWN AREA AND DENSITY YEAR BY YEAR. IT GIVES USERS THE CONVINIENCE OF TRANSPORTATION, ON THE OTHER HAND THE DIFFICULTY OF DESINING NETWORK. SO THIS PAPER AIMS AT ADDING “LEGIBILITY” TO THE NETWORK AND MAKING IT WORK AS A GEOGRAPHICAL PERCEPTION SYSTEM. THEREFORE, AS THE FIRST STEP, THIS PAPER INVESTIGATED HOW AND WHY USERS COGNIZE ON THE SUBWAY-NETWORK, AND ANALYZED THE STRUCTURE OF COGNITION AND MISTAKE. CONSIDERING THE ADVANTAGE OF THE FORMER AND THE DISADVANTAGE OF THE LATTER. WE SUGGESTED AN IDEA FOR PROMOTING “LEGIBILITY”（OF SKELETON STRUCTURE)OF CITY.