Generally, reinforcement clusters are formed in a composite. For the case that the rapture strain of the reinforcement in such a composite is smaller than that of the matrix, some of the reinforcements may break in the cluster when the composite is subjected to the external force. Thus the broken reinforcements and the unbroken reinforcements coexist within the cluster. Such a cluster can be regarded as a multi-phase inhomogeneity because the cluster contains different inhomogeneities corresponding to the broken and the unbroken reinforcements. From another viewpoint, the cluster can be regarded as a triple inhomogeneity because a crack exists in the reinforcement and the reinforcements are gathered to the cluster. Therefore, the reinforcement cluster in the composite can be modeled as a multi-phase triple inhomogeneity. As a first step, the multi-phase triple inclusion isolated in an infinite medium is taken into consideration in the present study and the average total strain, the average eigenstress and hence the average interaction strain induced in the multi-phase triple inclusion are derived by adopting the idea of the double inclusion method into the model.