Disclosed are a multi-connection system (MCS) and method for a service using an Internet protocol. The MCS includes a plurality of proxies; an MCS client to receive a packet to be transmitted from the client to the server, generate MCS packets by adding an MCS sequence identification (ID) to the packet, and sequentially and respectively transmit the MCS packets to the plurality of proxies, wherein a number of MCS packets corresponds to a number of pieces of proxy access information connected to the plurality of proxies or a set number of pieces of proxy access information; and an MCS server to respectively receive the MCS packets from the plurality of proxies; extract the MCS sequence IDs from the MCS packets, compare the extracted MCS sequence IDs with MCS sequence IDs stored beforehand; store the extracted MCS sequence IDs, generate server-receivable packets from the MCS packets, and transmit the server-receivable packets to the server when the extracted MCS sequence IDs are not identical to the stored MCS sequence IDs; and block the MCS packets from being transmitted to the server when the extracted MCS sequence IDs are identical to the stored MCS sequence IDs.