This report mainly discusses design problems of the interface for computer communication on the basis of the engineering task which needs to link the microcomputer Z80 and FACOM-230/38 remotely. The Fujitsu's BSC protocol is used. In this paper，the aspects in design of communication interface are discussed and some functions of the protocol are discussed，the formulas evaluating optimum length of the message block are deduced from effective line throughput，optimum division of the message block，usage of memory and so on. Finally，characteristics of the BSC protocol is analysed for communieation programming，the protocol is reali1ed by software and some communication program flow charts are presented.