To　investigate　how　human　brain　was　involved　in　explicit　rule　acquisition　during　problem　solving,　with　the　technique　of　fMRI,　we　used　a　task　of　simplified　Sudoku　solving　to　detect　the　change　of　brain　activity　from　a　freshman　to　a　rule-acquired　solver.　Brain　activities　in　the　lateral　prefrontal,　inferior　parietal　and　anterior　cingulated　cortex　increased　suggested　a　goal-directed　processing　with　more　accurate　representation　of　problem　state　and　more　efficient　rule　retrieval.　The　decrease　deactivation　in　the　medial　prefrontal　gyrus　might　relate　to　a　reduced　resource　allocation　in　the　later　stage;　and　the　signal　change　pattern　of　first　increasing　then　decreasing　in　the　superior　parietal　gyrus　might　suggest　a　sensible　response　for　attention　to　visual　perception　and　recognition　during　the　proceeds.　©　2012　Springer-Verlag.