Microcracks play vital roles in the prediction of the service life of concrete structure. Because microcracks in concrete structure are the preferential ingression channels for aggressive ions, e.g., chloride, sulphate, etc. However, microcracks have potentials to self-heal autogenously due to the continuous hydration of unhydrated cement, especially when ultra-/ high strength concrete is used. To quantify the autogenous self-healing effects of microcracks in cement paste, our experiment is designed to monitor the self-healing process of microcracks in cement paste continuously by using optical microscope. The healing products are quantified by image analysis with newly implemented software in MATLAB. The results indicate that the microcracks are not filled evenly along the crack length and most healing products are Ca(OH)2, which dissolve partly from the paste matrix and re-nucleate in the microcrack, in addition to its counterpart from the continuous hydration of unhydrated cement. Furthermore, the sample cracked at earlier age shows higher potential to heal, while the sample with smaller crack width experiences greater filling efficiency. The obtained autogenous selfhealing mechanism will be used in the future simulation. @en