The present invention provides a network data transmission method and system. The method comprises the steps of setting a plurality of data cache regions, wherein the plurality of data cache regions are equipped with different time thresholds and time delay ranges respectively and correspondingly; identifying a received small data packet to obtain the cacheable time of the small data packet, and caching the small data packet in the data cache region corresponding to the time delay range to which the cacheable time belongs; blocking the small data packet cached in each data cache region to form a large data packet of which the size is not greater than the size of a maximum transmission unit; when each data cache region starts to count down from the respective time threshold, forwarding the formed large data packet out when the countdown reaches a preset value, wherein the time difference of the time threshold of each data cache region and the preset value is not greater than a minimum value in the respective time delay range. According to the network data transmission method and system provided by the present invention, the data transmission rate can be improved while the time delay requirements of various business types are satisfied.