The current study explored the effect of retention of working memory content on time judgment by manipulating the validity of WM content. We used irregular objects as experimental stimuli, and made the object during duration judgment match the WM content or not. In Experiment 1, using a dual task paradigm combing working memory and time judgment task, we asked participants first to memorize an object, and indicate whether a test object changed at the end of each trial. During the delay period, participants had to judge which of two successive objects was presented longer (or shorter). In Experiment 2, participants were required to ignore the first object, and only to perform time judgment task. The results revealed that in comparison with single timing task, retention of WM content prolonged the decision time of duration judgment. Furthermore, in memory-matching and perception-matching conditions, there were lower precision and longer decision time when matching stimuli had a longer duration than mismatching ones, as compared to when matching objects had a shorter duration than mismatching ones. This study suggests that maintenance of WM information did increased the difficulty of decision, WM content-based interference might be caused by attentional orientation derived from WM content.