A method for call proceeding in call control of an application server, comprising: the application server sending a first Offer message to a second party after making a media negotiation with a first party; the application server receiving a first Answer message sent from the second party in response to the first Offer message, transforming the received first Answer message into a second Offer message and then sending the second Offer message to the first party, wherein, the second Offer message carries a confirmation request for a Precondition state of the first party; the application server receiving a second Answer message sent from the first party in response to the second Offer message, wherein, the received second Answer message carries a confirmation response to the Precondition state from the first party; characterised in that when determining that the received second Answer message meets a condition for transforming the received second Answer message, the application server transforming the received second Answer message into a third Offer message and then sending the third Offer message to the second party, wherein, the third Offer message carries the confirmation response to the Precondition state from the first party, wherein, the condition for transforming the received second Answer message comprises a first transforming condition and/or a second transforming condition; wherein, the first transforming condition comprises: a level required for the Precondition state is mandatory; the confirmation request for the Precondition state of the first party exists in the first Answer message; and the Precondition state in the second Answer message meets the Precondition state in the confirmation request for the Precondition state of the first party; the second transforming condition comprises: a confirmation request for a Precondition state of the second party exists in the second Answer message, and a current Precondition state of the second party, received in the first Answer message from the second party, does not meet the Precondition state in the confirmation request of the second Answer message. the application server sending a first Offer message to a second party after making a media negotiation with a first party; the application server receiving a first Answer message sent from the second party in response to the first Offer message, transforming the received first Answer message into a second Offer message and then sending the second Offer message to the first party, wherein, the second Offer message carries a confirmation request for a Precondition state of the first party; the application server receiving a second Answer message sent from the first party in response to the second Offer message, wherein, the received second Answer message carries a confirmation response to the Precondition state from the first party; characterised in that when determining that the received second Answer message meets a condition for transforming the received second Answer message, the application server transforming the received second Answer message into a third Offer message and then sending the third Offer message to the second party, wherein, the third Offer message carries the confirmation response to the Precondition state from the first party, wherein, the condition for transforming the received second Answer message comprises a first transforming condition and/or a second transforming condition; wherein, the first transforming condition comprises: a level required for the Precondition state is mandatory; the confirmation request for the Precondition state of the first party exists in the first Answer message; and the Precondition state in the second Answer message meets the Precondition state in the confirmation request for the Precondition state of the first party; a level required for the Precondition state is mandatory; the confirmation request for the Precondition state of the first party exists in the first Answer message; and the Precondition state in the second Answer message meets the Precondition state in the confirmation request for the Precondition state of the first party; the second transforming condition comprises: a confirmation request for a Precondition state of the second party exists in the second Answer message, and a current Precondition state of the second party, received in the first Answer message from the second party, does not meet the Precondition state in the confirmation request of the second Answer message.