A 6-bit wideband high accuracy active phase shifter with 6~18 GHz frequency range was designed. The passive baluns, poly-phase filters, vector-sum cells and digital controlled cells were included in the proposed phase shifter. This phase shifter was implemented in a 55 nm CMOS process. The overall chip size was 1.29 mm×0.9 mm, and the phase shifter core chip size was 1.02 mm×0.58 mm. The post-simulation results showed that the RMS gain variation was less than 1 dB, and the RMS phase error was less than 0.75° within 6~18 GHz frequency range. The input and output return losses were less than -8.5 dB and -10 dB, and the total power consumption was 20.7 mW. The relative bandwidth of the 6 bit phase shifter was 100%, covering C, X and Ku band. It was suitable for radar detection and other applications.