Abstract: With the ground-based detection system in China, limited by the site layout, it is difficult to realize the target detection and tracking in the full orbit space. For implementing the full-time detection and tracking of neighbourhood space targets for high-value spacecraft, we propose an approach using the miniaturized phased array radar based on the concomitant micro-nano satellite. By comparing the performances of different band radars in the searching and fine tracking of large-scale space targets, and considering the factors concerning the system complexity and the power consumption, the C band is selected as the working band of the radar. In this paper, the design of the miniaturized phased array radar system is presented, including the signal processing method for the target search and tracking, and the error analysis of the ranging and angle measurement. The simulation results show that the miniaturized phased array radar is capable of searching the three-dimensional space targets in the range of 40°×40° and 25 km, with a ranging accuracy of less than 0.4 m and an angle measuring precision of not more than 0.03°, and the requirements of large-scale search and tracking of space targets can be met.