Tenant separation is a provision for cloud computing to be provided to tenants as a third party service, therefore the tenants' confidence in the security effectiveness of cloud tenant is critical to the promotion of cloud services. However, in a third party service such as cloud computing, tenants have few opportunities to take part in the construction and management of the infrastructure of cloud computing, making it hard for the tenants to trust the tenant separation mechanism in cloud. This paper views the transparency requirement as a part of trusted cloud tenant separation mechanism, implements a cloud tenant separation mechanism and its transparency requirement based on the inter-domain information flow control policy in cloud computing systems, and proves that the resulting cloud tenant separation mechanism is secure and effective by non-interference theory.