The present invention provides a method for implementing an Unstructured Supplementary Service Data (USSD) service in a Code Division Multiple Access (CDMA) network, which is implemented based on a mobile intelligent network service and a flash message service. A Mobile Switching Center (MSC) triggers the mobile intelligent network service, a Service Control Point (SCP) determines an operation type code of the current step according to a user identification and a USSD access code and performs a corresponding operation, and at the same time constructs short message content associated with the operation type code of the current step, and transmits the short message content to a Mobile Station (MS) by way of the flash message. The present invention also correspondingly provides a system and device for implementing a USSD service in a CDMA network. By providing an operation prompt, the present invention realizes real-time message interaction, and reduces user's misoperation effectively.