Non-public networks (NPNs) have drawn much attention due to their flexibility and efficiency with B5G. According to the requirements of various application scenarios, NPNs can be tailored to a number of deployments, sharing the B5G system totally or in part. The isolation of NPNs is a critical issue. This paper provides a survey of isolation schemes for B5G NPNs. First, we present an overview of various deployments and the corresponding isolation demands for B5G NPNs. To meet these isolation demands, three kinds of NPN isolation—i.e., spectrum isolation, RAN isolation and CN isolation—are discussed. Then, the corresponding isolation technologies are introduced and analyzed. Finally, open research challenges, such as wireless throughput capacity with spectrum isolation, operation with isolation requirements and data isolation of software-defined CN for B5G NPNs, are discussed.