The effects of magnesia and calcium sulphoaluminate expansive agent on hydration products and microstructure of engineered cementitious composites were studied. The results show that the two expansive agents decrease the fluidity and mechanical properties. The addition of magnesia expansion agent makes a large amount of magnesium-rich calcium-silicate in the material system, while the addition of calcium sulfoaluminate expansion agent increases the content of ettringite in the material system. The two hydration products refine the pore structure of the material and improve the impermeability of the samples. The pore diameter of the sample dope with 5% (mass fraction) calcium sulfoaluminate expansion agent is smaller than that with magnesia expansive agent, and the structure of sample with calcium sulfoaluminate expansion agent is more stable.