Single-Walled Carbon Nanotubes(SWNTs) have excellent electrical properties to fabricate field-effect transistor (FET) biosensor, microelectrodes, microelectric unit etc. At present, biosensors based on CNTFET are required in various applications, including clinical diagnostics, environmental testing, food analysis, and bioterrorism detection technologies. But nowadays SWNTs are typically grown as mixtures of metallic-SWNTs and semiconducting-SWNTs, which limited their further application. In this paper, we reported a simple, scalable way to separate SWNTs by using HNO3/H2SO4, and discussed the factors which influenced the separation. At last, we fabricated SWNTs FET biosensor with treated SWNTs by applying AC dielectrophoresis (ACDEP) method.