The invention discloses a hierarchical routing query method of an automatic switched optical network. After a RC of a subdomain network element receives a query request, the RC of the subdomain network element finishes the routing calculation, if the complete routing fails to be obtained, the RC of the subdomain network element transfers the request to a parent domain RC and the calculated partialrouting is carried; the parent domain RC finishes the routing calculation based on the node RDB, if the complete routing fails to be obtained, the parent domain RC transfers or broadcasts the requestto a certain other subdomain RC one by one and the routing among the subdomains and the routing of the subdomain initiating the request are saved; the subdomain RC finishes the routing calculation and returns the routing query result to the parent domain RC; if the parent domain RC can obtain or combinedly obtain the complete routing, the parent domain RC returns the routing to the request party;if the parent domain RC still does not obtain the complete routing after the return results of all the subdomains are received, the parent domain RC returns the routing query failure information to the request party. The invention can solve the problem of establishing the routing query of cross-domain connection, and has the advantage of quick query.