As　one　of　the　main　items　of　RoboCup,　Sony　four-legged　robot　soccer　is　the　technical　foundation　and　previous　process　of　the　biped　robot　soccer.　The　Sony　four-legged　robot　soccer　is　also　a　typically　dynamic　multi-agent　system;　and　so　it　is　important　to　research　work　of　robotics.　The　development　of　the　RoboCup　game　and　the　research　is　reviewed.　The　modularization　technique　is　used　to　design　the　whole　software　system　of　four-legged　robot.　By　dividing　the　software　system　into　four　modules,　the　system　structure,　the　main　function　and　realization　of　every　module　are　presented.