In order to promote the diversified utilization of recycled brick concrete aggregate with different particle sizes, recycled brick concrete fine aggregate was used to completely replace quartz sand, and mixed with different content of polypropylene fiber to prepare recycled brick concrete engineering cementitious composites (ECC). The effects of failure characteristics, strength influence mechanism and microstructure on mechanical properties were studied. The results show that the failure mode of specimens without fiber is brittle failure, and recycled brick concrete ECC with fiber has obvious strain hardening characteristics during tensile stress. With the increase of fiber content, the flexural strength, ultimate tensile strength and ultimate tensile strain of recycled brick concrete ECC continue to increase, and the compressive strength increases first and then decreases, which shows good ductility and ductile failure characteristics. The porosity of recycled brick concrete ECC is 11.28%~13.68%. Fiber has good bonding property with recycled brick concrete ECC observed by SEM, the fiber failure modes are mainly pull-out and tensile failure, and the strain hardening tensile amplitude and tensile strength after cracking are lower than that of ordinary ECC concrete. The interface bonding property of old and new mortar is relatively weak, and micro-cracks are easy to occur and develop in the interface transition zone during failure.