A relay transmission method, wherein the method comprises: receiving, by a relay terminal, broadcast messages sent by N vehicle terminals, wherein the broadcast messages comprise vehicle location information, and N is an integer greater than 1; determining, by the relay terminal, based on the vehicle location information in the received broadcast messages, a vehicle existing between a vehicle terminal i of the N vehicle terminals and a vehicle terminal j of the N vehicle terminals; calculating, by the relay terminal, link quality of a communication link R ij based on vehicle size information corresponding to the vehicle, wherein the R ij is a communication link used when the vehicle terminal i and the vehicle terminal j communicate with each other; and if the link quality of the R ij is lower than a preset threshold, forwarding, to the vehicle terminal j, a to-be-forwarded broadcast message sent by the vehicle terminal i, and forwarding, to the vehicle terminal i, a to-be-forwarded broadcast message sent by the vehicle terminal j; wherein when the link quality of the R ij is lower than the preset threshold, the method further comprises: - predicting duration for which the link quality of the R ij is lower than the preset threshold, based on the vehicle, vehicle driving information corresponding to the vehicle terminal i, and vehicle driving information corresponding to the vehicle terminal j; and - within the duration, directly forwarding, to the vehicle terminal j, the to-be- forwarded broadcast message sent by the vehicle terminal i, and directly forwarding, to the vehicle terminal i, the to-be-forwarded broadcast message sent by the vehicle terminal j, to reduce calculation load of the relay terminal; wherein the vehicle driving information comprises vehicle driving speed information and vehicle driving direction information. receiving, by a relay terminal, broadcast messages sent by N vehicle terminals, wherein the broadcast messages comprise vehicle location information, and N is an integer greater than 1; determining, by the relay terminal, based on the vehicle location information in the received broadcast messages, a vehicle existing between a vehicle terminal i of the N vehicle terminals and a vehicle terminal j of the N vehicle terminals; calculating, by the relay terminal, link quality of a communication link R ij based on vehicle size information corresponding to the vehicle, wherein the R ij is a communication link used when the vehicle terminal i and the vehicle terminal j communicate with each other; and if the link quality of the R ij is lower than a preset threshold, forwarding, to the vehicle terminal j, a to-be-forwarded broadcast message sent by the vehicle terminal i, and forwarding, to the vehicle terminal i, a to-be-forwarded broadcast message sent by the vehicle terminal j; wherein when the link quality of the R ij is lower than the preset threshold, the method further comprises: - predicting duration for which the link quality of the R ij is lower than the preset threshold, based on the vehicle, vehicle driving information corresponding to the vehicle terminal i, and vehicle driving information corresponding to the vehicle terminal j; and - within the duration, directly forwarding, to the vehicle terminal j, the to-be- forwarded broadcast message sent by the vehicle terminal i, and directly forwarding, to the vehicle terminal i, the to-be-forwarded broadcast message sent by the vehicle terminal j, to reduce calculation load of the relay terminal; - predicting duration for which the link quality of the R ij is lower than the preset threshold, based on the vehicle, vehicle driving information corresponding to the vehicle terminal i, and vehicle driving information corresponding to the vehicle terminal j; and - within the duration, directly forwarding, to the vehicle terminal j, the to-be- forwarded broadcast message sent by the vehicle terminal i, and directly forwarding, to the vehicle terminal i, the to-be-forwarded broadcast message sent by the vehicle terminal j, to reduce calculation load of the relay terminal; wherein the vehicle driving information comprises vehicle driving speed information and vehicle driving direction information.