A new concept of ambiguity resolution, called dual-space ambiguity resolution approach(DARA), i.e. searching in two spaces at the same time, is presented. It shows DARA can dramatically reduce the ambiguity candidates even if the C/A codes are used and faster than in an individual space, because only few ambiguity candidates meet the conditions of the two spaces simultaneously. The result of vehicle test shows that the new approach performs perfectly. Compared to the traditional RTK, millimetre level of the KINRTK is achieved.