At present， piezoelectric actuated multi-legged micro-crawling robots manufactured by smart composite microstructure （SCM） technology typically employ an integral design and assembly approach. Although this results in a compact structure of the robots with high integration， it leads to significant coupling in structure and challenge in assembly and maintenance. To address this issue， this paper proposes a design method reflecting in modular-manufacturing and free-assembly for multi-legged micro-crawling robots， and develops a quadruped micro-crawling robot with horizontal-modular layout feature accordingly. First， the modular design scheme for the entire robot system and the specific structure of multi-degree-of-freedom leg are presented. Second， the manufacturing and assembly processes of the piezoelectric actuating module， the angular-motion micro module， and the two-degree-of-freedom leg are analyzed， and the actual manufacturing and testing for each module are completed. Third， a micro-robot prototype is assembled， and its locomotion simulation based on the Trot gait is analyzed by using Adams software. Finally， the locomotion testing of the micro-crawling robot is conducted to preliminarily validate the corresponding performance. It provides a foundation for subsequent optimization design and the development of more versatile modular micro-crawling robots.