An isolation NLDMOS device including: an N well and a P well adjacent to each other on an upper part of a P substrate; on the upper part of the P well are sequentially arranged a first P type heavily doped region, a first field oxide, and a second P type heavily doped region; on the upper part of the N well are arranged a second field oxide and an N type heavily doped region; a gate oxide is between the second P type heavily doped region and the second field oxide; a gate polysilicon sits above the gate oxide and part of the second field oxide; from the first P type heavily doped region, the second P type heavily doped region and the N type heavily doped region are led out each a connecting wire via a respective contact hole.