The invention relates to a prefabricated fabricated composite wall body combining connecting system and an application construction method thereof. The prefabricated fabricated composite wall body combining connecting system comprises an I-shaped connecting piece and a connecting piece shaped like a Chinese character 'ji'. The I-shaped connecting piece comprises a first flange, a second flange and a web plate, the web plate is located between the first flange and the second flange and connected with the first flange and the second flange, and circular holes are formed in the first flange and the second flange correspondingly. Anti-shearing steel ribs are arranged in the circular holes in a penetrating mode. The connecting piece shaped like the Chinese character 'ji' comprises a first horizontal connecting rod and two second horizontal connecting rods. The second horizontal connecting rods are formed by means of the method that the two ends of the first horizontal connecting rod extend in the direction perpendicular to the first horizontal connecting rod and then bend in the opposite directions correspondingly. The prefabricated fabricated composite wall body combining connecting system is small in heat conductivity coefficient, good in corrosion resistance, high in anti-shearing performance and convenient to mount. The application construction method of the prefabricated fabricated composite wall body combining connecting system is easy to operate and suitable for application and popularization.