Self-regulation is a key point for success; however, self-regulation failure happened more often. Baumeister and his colleagues proposed an ego-depletion model for this phenomenon. According to this model, self-regulation need energy which is similar to muscle’s strength and it is limited. The energy will lost temporally when an individual do a self-control task and that is so called ego-depletion. Then people’s performance in the second task which needs self-regulation will get worse. Recently, many researchers demonstrate that not only self-regulation but also executive function both needs resources. That is to say, ego-depletion may hinder executive function’s working. Working memory is well known as a main component of executive function, will it be influenced by ego-depletion? This study included two experiments. Experiment 1 examined the effect of ego-depletion on WM. 40 sixth graders (20 boys, 20 girls) were randomly divided into experimental group and control group and reacted to color-word stroop depleting task or non-depleting task respectively. Then all subjects completed working memory span tasks. The result showed that ego-depletion task impaired working memory, and the capacity of working memory of experimental group decreased significantly comparing with the control group. Experiment 2 investigated whether the negative effect of ego-depletion on working memory could be eliminated by positive emotion. Subjects were 40 sixth graders (21 boys, 19girls). They were randomly divided into experimental group and control group and both groups reacted to color -word stroop depleting task first. Then positive emotion was priming using autobiographical memory in experimental group, at the same time control group had a rest for three minutes. Finally, all subjects completed the working memory span task. The result showed the working memory capacity of experimental group was significant larger than that of control group and there was no difference comparing with the non-depletion group in experiment 1. Conclusions: (1) Ego-depletion had negative influence on working memory; the capacity of working memory would decline quickly when subjects suffered ego-depletion. (2) The negative effect of ego-depletion on working memory could be eliminated by positive emotion.