Abstract: Addressing the issue of difficulty in simultaneously reducing amplitude and phase errors in variable gain amplifiers, a digital variable gain amplifier for phased array system is designed based on Si-based process. A digital control current steering array structure is proposed, whose resistance ratio of each branch determines the gain step, and the resistance is less disturbed by the PVT, which reduces the gain error brought by the PVT. In addition, the structure realizes the distribution of the current by digitally controlling the current of each branch to selectively pass the current, thus accurately controlling the gain and improving the gain accuracy. At the same time, a cross-coupled capacitor structure is introduced to reduce the additional phase shift under the premise of ensuring the gain. The post-simulation results show that the variable gain amplifier achieves a gain variation range of 17.7 dB and a gain step of 1 dB, a gain flatness within 0.5 dB, a maximum gain of more than 11 dB, a gain step error of less than ±0.1 dB, and an additive phase shift of less than ±3.5° over the frequency range of 24 - 29.5 GHz.