With the rapid development of information technology, more and more requesters need accessing the services in different access domains, which make the access process in cross-domain become more difficultly. The traditional access control models couldn’t solve the access process for their design limitations and diversity access policies. Usage control model (UCON) was proposed to strengthen the expression of access control model, but UCON is only a conceptual model. How to use the UCON in access process? It is worthwhile to further study. Extensible access control markup language (XACML) is an open standard XML-based language, which can be used to describe the security policy. In order to solve the access process in different access domains, based on XACML, access process of data-flow in cross-domain usage control model is proposed in the paper. Access process of data-flow cross different domains in XACML is introduced to solve the cross-domain problem. Finally, a small example is given to verify the effectiveness of access process.