File transmission method and instant messaging terminal and system

The invention discloses a file transmission method and an instant messaging terminal and system. The file transmission method and the instant messaging terminal and system aim at solving the problems that under a poor network environment, when a network is interrupted in file transmission of existing instant messaging software, exceeding human intervenes are needed, efficiency is low, and user experience is not good. The file transmission method provides an interruption automatic retransmission configuration option, an interruption automatic receiving configuration option and an interruption automatic retransmission off-line file configuration option for the instant messaging terminal, so when a file is interrupted in transmission, the instant messaging system can automatically retransmit or continue transmitting the file interrupted in transmission, and file transmission efficiency is thereby improved.