DNA　computing　is　a　means　of　solving　a　class　of　intractable　computational　problems,　in　which　the　computing　time　can　grow　exponentially　with　problem　size.　Based　on　the　Adleman-Lipton　model,　some　grouping　strategy　and　the　corresponding　operations　are　designed　to　study　the　commonly　algorithm　model　of　3-SAT　in　DNA　computing.　A　parallel　algorithm　is　proposed　to　control　the　running　time　of　algorithm　to　constant.