Lightweight and high ductility cementitious composite was developed as a fire-resistive coating (FR-ECC) with domestic raw materials. The feasibility of FR-ECC as fire-resistive coating was demonstrated. The mechanical properties of FR-ECC with different proportions were investigated via axial tensile test and compressive test. The cooperative deformation performance of FR-ECC and steel member was determined via four-point bending beam test. The results indicate that FR-ECC with three proportions has the characteristics of multi-cracking and strain-hardening with an average tensile strength of 1.30 MPa and an average strain capacity of 1.93%. The results of compressive test show a high compressive deformation capacity of FR-ECC with an average strength of 3.99 MPa. The tensile and compressive properties can be enhanced by increasing the fiber content. According to the results of the four-point bending beam test, FR-ECC can adapt to a larger bending deformation as the coating thickness decreases. When the coating thickness is no more than 10 mm, FR-ECC can produce some fine cracks with the deformation of the steel beam instead of delaminating or falling off. FR-ECC has a capability of cooperative deformation with steel member under a complex stress.