A method for transmitting data, the method executed by a core network control entity, the method comprising: determining, after receiving a first message sent by a user equipment, whether first indication information is set, wherein the first indication information indicates that a server buffers downlink data to be sent to the user equipment; and when determining that the first indication information is set, retaining a signaling connection to the user equipment, and triggering the server that buffers the downlink data to send the downlink data to the user equipment; wherein the triggering the server that buffers the downlink data to send the downlink data to the user equipment comprises: sending a downlink data delivery request message to the server that buffers the downlink data, so as to trigger the server that buffers the downlink data to send the downlink data to the user equipment; the retaining a signaling connection to the user equipment comprises: sending a second message comprising second indication information to the user equipment, wherein the second indication information indicates that there is data to be sent to the user equipment, so as to retain the signaling connection to the user equipment; characterized in that the method further comprises: when determining that the first indication information is not set, sending a third message comprising third indication information to the user equipment, wherein the third indication information indicates that there is no downlink data to be sent to the user equipment, so that the user equipment disables a receiver or enters a power saving mode or shuts down according to the third indication information. determining, after receiving a first message sent by a user equipment, whether first indication information is set, wherein the first indication information indicates that a server buffers downlink data to be sent to the user equipment; and when determining that the first indication information is set, retaining a signaling connection to the user equipment, and triggering the server that buffers the downlink data to send the downlink data to the user equipment; wherein the triggering the server that buffers the downlink data to send the downlink data to the user equipment comprises: sending a downlink data delivery request message to the server that buffers the downlink data, so as to trigger the server that buffers the downlink data to send the downlink data to the user equipment; the retaining a signaling connection to the user equipment comprises: sending a second message comprising second indication information to the user equipment, wherein the second indication information indicates that there is data to be sent to the user equipment, so as to retain the signaling connection to the user equipment; characterized in that the method further comprises: when determining that the first indication information is not set, sending a third message comprising third indication information to the user equipment, wherein the third indication information indicates that there is no downlink data to be sent to the user equipment, so that the user equipment disables a receiver or enters a power saving mode or shuts down according to the third indication information. sending a downlink data delivery request message to the server that buffers the downlink data, so as to trigger the server that buffers the downlink data to send the downlink data to the user equipment; the retaining a signaling connection to the user equipment comprises: sending a second message comprising second indication information to the user equipment, wherein the second indication information indicates that there is data to be sent to the user equipment, so as to retain the signaling connection to the user equipment; characterized in that the method further comprises: when determining that the first indication information is not set, sending a third message comprising third indication information to the user equipment, wherein the third indication information indicates that there is no downlink data to be sent to the user equipment, so that the user equipment disables a receiver or enters a power saving mode or shuts down according to the third indication information.