A data transmission method to be applied to a source client, wherein the source client is a client in a foreground running state in a mobile terminal, the mobile terminal, by means of a split-screen function, divides a display screen thereof into a first split screen for displaying a running interface of the source client and a second split screen for displaying a running interface of a target client, and the target client is a client in a foreground running state in the mobile terminal, the method comprises: establishing a communication connection between the source client and the target client in the case that a preset condition of establishing a communication connection is satisfied; receiving a drag instruction for a thumbnail of target data in the source client and moving the thumbnail according to the drag instruction; determining a location T 1 of the thumbnail on the first split screen and a portion to be displayed D S1 of the thumbnail on the first split screen according to the drag instruction, displaying the portion to be displayed D S1 at the location T 1, and sending location information of the thumbnail and a pattern of the thumbnail to the target client through the established communication connection so that the target client determines a location T 2 of the thumbnail on the second split screen and a portion to be displayed Ds2 of the thumbnail on the second split screen according to the received information and displays the portion to be displayed D S2 at the location T 2 (S 105), wherein the portion to be displayed D S1 and the portion to be displayed Ds2 constitute the whole of the thumbnail; monitoring whether a data transmission instruction for the target data is received if the data transmission instruction is received, transmitting the target data to the target client through the established communication connection, wherein the step of monitoring whether a data transmission instruction for the target data is received comprises: monitoring whether a ratio of the portion to be displayed D S2 of the thumbnail displayed on the second split screen to the whole of the thumbnail is greater than a preset ratio threshold when a release operation on the thumbnail is performed by a user; if yes, determining that the data transmission instruction for the target data is received. establishing a communication connection between the source client and the target client in the case that a preset condition of establishing a communication connection is satisfied; receiving a drag instruction for a thumbnail of target data in the source client and moving the thumbnail according to the drag instruction; determining a location T 1 of the thumbnail on the first split screen and a portion to be displayed D S1 of the thumbnail on the first split screen according to the drag instruction, displaying the portion to be displayed D S1 at the location T 1, and sending location information of the thumbnail and a pattern of the thumbnail to the target client through the established communication connection so that the target client determines a location T 2 of the thumbnail on the second split screen and a portion to be displayed Ds2 of the thumbnail on the second split screen according to the received information and displays the portion to be displayed D S2 at the location T 2 (S 105), wherein the portion to be displayed D S1 and the portion to be displayed Ds2 constitute the whole of the thumbnail; monitoring whether a data transmission instruction for the target data is received if the data transmission instruction is received, transmitting the target data to the target client through the established communication connection, wherein the step of monitoring whether a data transmission instruction for the target data is received comprises: monitoring whether a ratio of the portion to be displayed D S2 of the thumbnail displayed on the second split screen to the whole of the thumbnail is greater than a preset ratio threshold when a release operation on the thumbnail is performed by a user; if yes, determining that the data transmission instruction for the target data is received. monitoring whether a ratio of the portion to be displayed D S2 of the thumbnail displayed on the second split screen to the whole of the thumbnail is greater than a preset ratio threshold when a release operation on the thumbnail is performed by a user; if yes, determining that the data transmission instruction for the target data is received.