In order to design man-machine system, communication system and other tasks that require information, we need to understand the characteristics of hyman short-term memory (STM). Thus, the purpose of this thesis is to investigate the influences of information stress and retention time on human performances and their relation- ships for STM of visual invormation. Eight subjects performed the computer monitering with STM task. The results showed that performance on serial recall from STM get wores and response time (and completion time) on information transmission by recall from STM increase as information stress and retention time increase. Also, there existed inverse proportional relationship between recall performance and response time (and completion time).