Abstract: In order to solve the problem of slow repair efficiency of current microbial repair materials,sodium alginate is used to modify exist‐ing microbial repair materials,and a new external repair material with fast and high efficiency is developed.The basic properties and repair effects of the repair material are explored.The results show that the repair material with sodium alginate has good Ca²⁺ adsorption and can re‐pair mortar cracks with a width of 1.5 mm and depth of 20 mm only once.The repair products are mainly calcium alginate and calcium carbon‐ate,filling the cracks together.The flexural strength increases by 20%compared to before repair,which is restored from 3.5 MPa to 4.2 MPa.