The present invention is the method for mobile double-mode system to provide trans-network call failure sound. First, in the double-mode connecting gateway, different sound signals are configured for different failures of roaming user; and then, when the connecting gateway receives roaming network responded call failure message, it sends corresponding sound signal to the attribute network based on different failures. Thus, the attribute network can establish phonetic channel for the calling side according to the sound number. The present invention leads the treatment of failure to normal phonetic succession and provides correct sound prompt for the calling party in called failure simply and directly.