Embodiments of the present invention relate to a route decision method, a content delivery apparatus, and a content delivery network interconnection system. A route decision method includes: receiving a notification message sent by a downstream CDN; determining a current service aggregate according to the notification message; and according to the current service aggregate and a total service quantity thresholdtotal quantity of services, performing route decision on a to-be-forwarded user request, where the total service quantity thresholdtotal quantity of services is an upper limit, set by the downstream CDN, of services capable of being provided by the downstream CDN for an upstream CDN. The embodiments of the present invention improve the accuracy of an upstream CDN in selecting a downstream CDN for a to-be-forwarded user request, and thereby improve the route decision efficiency.