Abstract: A data compression method and data communication system utilizing the same includes: a sender apparatus that compares, in response to input of data to be sent, the input data with the previously sent data in storage. The sender apparatus produces, when a data item repeated in the input data and previously sent data is found, delta data by excluding the repeated data item from the input data. The sender apparatus represents the delta data in a transport format, and transmits the delta data. The system includes a receiver apparatus that receives the data in a transport format. The receiver apparatus adds, when delta data is present in the received data, a repeated data item to the delta data, and recovers the original data. The sender apparatus sends and receives data to and from the receiver apparatus through a text-based protocol.