While silver-based sintered materials are limited by cost and electromigration, and copper faces challenges with oxidation at high temperatures, Cu-based composite sintering materials offer promising alternative solutions. This review examines recent advances in Cu-based composite sintered materials for die-attach in power electronics packaging, focusing on their mechanical, thermal, electrical properties, and reliability. This review systematically categorizes such compounding strategies, including direct mixing, core-shell structures, and alloying, analyzing the impact on composite properties. Furthermore, the reliability of Cu-based composite sintered joints is evaluated, addressing high-temperature storage, thermal cycling, corrosion, and electrochemical migration. Challenges such as oxidation resistance, process optimization, and cost-effectiveness are discussed, together with future research directions. This work aims to support researchers in advancing Cu-based composite sintering materials research and development, broadening material options for high-temperature power electronics packaging applications.