Abstract: In 　this　paperthe 　traditional 　objective 　functionthe　quadratic　of 　difference 　of 　float 　ambiguity　and 　inte ger 　ambiguit yis 　re placed 　by　a　modified　function 　called 　sum　of 　L1and　L2pure 　carrier 　phaseresidua 　squares　when　searching　for 　a　correct 　inte ger 　ambiguit y．The　inte ger 　ambiguities 　search 　space is 　obtained　by　a　floatin g　transformation 　and　building　observation　model　with　DDdouble　difference CA　code 　range　and　wide 　lane 　carrier 　phase．The　calculation 　results 　from　18－hour　static　GPS　data 　indicate 　that 　the　modified　is 　better 　than 　the 　traditional 　objective 　function 　for 　reliabilit y　and　usabilit y　with　a hi gher 　success 　rate．