The fragile cementitious materials can be easily cracked under service in the harsh environment, which can reduce the loading capacity of concrete structures and its expected service life. The self-curing ability of cementitious materials is thus essential for the resilience of the concrete structures in harsh environments. The purpose of the study is to enhance the self-healing ability of Engineered Cementitious Composites (ECC) in harsh environment though cementitious matrix optimization and crack width controlling. The cementitious matrix containing cement, silica fume, and fly ash is optimized based on the Simple Centroid Method. The Ultra-high Molecular Weight Polyethylene (UHMWPE) fibers have been selected as reinforcing materials due to their superior mechanical performance. The results show that the compressive strength of the ECC samples generally increases with the silica fume content, and the tensile strength rises with both the silica fume and cement content. Meanwhile, the ultimate tensile strain of the ECC samples increases and declines with the fly ash and silica fume content, respectively. The self-repairing properties of the pre-damaged ECC specimens with 5 % strain are examined through exposure in the simulated harsh environment. It is found that the exposure to the groundwater environment can improve the self-curing ability of the pre-damaged ECC specimens, while the self-curing ability can be deteriorated under exposure to the marine environment. Furthermore, the crack sealing and strength recovery ability of cementitious materials can be enhanced with higher fly ash content and lower silica fume content. Finally, the self-curing mechanism of the ECC samples is analyzed by means of the phase and microstructure analysis. Exposure to groundwater environments can promote the generation of the C–S–H gel and calcium carbonate in the self-curing product, and thus enhance the self-healing efficiency. This study can contribute the resilience enhancement of the concrete structure in harsh environments.