Modular datacenters (MDC) use shipping containers as large pluggable building blocks for mega-datacenter. Although it simplifies the construction and maintenance of mega-datacenters, interconnecting hundreds or even thousands of containers is still challenging. In this paper, we present a high cacpacity and fault-tolerant inter-container datacenter network based on Kautz graph, called iCautz. Based on iCautz's topology, we propose the single-path and fault tolerant routing algorithm. The theoretical analysis and simulations show that the network performance is of iCautz as well as MDCube, and it behaves much better than MDCube on fault-tolerance. When 10% servers fail, iCautz's throughput drops by 14.3% When 10% switches fail, its throughput drops byonly 6.2%.