A data forwarding method in S1 handover, comprising steps of: receiving, by a source side mobility management entity, a handover request, and sending, by the source side mobility management entity, a message to stop data sending to a source side service gateway; stopping, by the source side service gateway, sending data to a source side E-URTAN Node B, eNB, after the source side service gateway receives the message to stop data sending, and caching, by the source side service gateway, the data; configuring, by the source side mobility management entity, a forward tunnel between a target side service gateway and the source side service gateway after the source side mobility management entity receives a Forward Relocation Response; and forwarding, by the source side service gateway, the cached data to a target side eNB via the forward tunnel and the target side service gateway; the method further comprising: before the step of configuring, by the source side mobility management entity, a forward tunnel between the source side service gateway and a target side service gateway after the source side mobility management entity receives a Forward Relocation Response, sending, by the source side mobility management entity, a Forward Relocation Request to a target side mobility management entity; and configuring, by the target side mobility management entity, a forward tunnel between the target side service gateway and the source side service gateway, and sending, by the target side mobility management entity, a handover request to the target side eNB; after the step of receiving a handover request to the target side eNB, sending, by the target side eNB, a Handover Request Acknowledge to the target side mobility management entity after the target side eNB configures a forward tunnel; and configuring, by the target side mobility management entity, a forward tunnel between the target side service gateway and the target side eNB, and sending, by the target side mobility management entity, the Forward Relocation Response to the source side mobility management entity. receiving, by a source side mobility management entity, a handover request, and sending, by the source side mobility management entity, a message to stop data sending to a source side service gateway; stopping, by the source side service gateway, sending data to a source side E-URTAN Node B, eNB, after the source side service gateway receives the message to stop data sending, and caching, by the source side service gateway, the data; configuring, by the source side mobility management entity, a forward tunnel between a target side service gateway and the source side service gateway after the source side mobility management entity receives a Forward Relocation Response; and forwarding, by the source side service gateway, the cached data to a target side eNB via the forward tunnel and the target side service gateway; the method further comprising: before the step of configuring, by the source side mobility management entity, a forward tunnel between the source side service gateway and a target side service gateway after the source side mobility management entity receives a Forward Relocation Response, sending, by the source side mobility management entity, a Forward Relocation Request to a target side mobility management entity; and configuring, by the target side mobility management entity, a forward tunnel between the target side service gateway and the source side service gateway, and sending, by the target side mobility management entity, a handover request to the target side eNB; after the step of receiving a handover request to the target side eNB, sending, by the target side eNB, a Handover Request Acknowledge to the target side mobility management entity after the target side eNB configures a forward tunnel; and configuring, by the target side mobility management entity, a forward tunnel between the target side service gateway and the target side eNB, and sending, by the target side mobility management entity, the Forward Relocation Response to the source side mobility management entity.