To control negative emotion entails avoiding the harmful influences of bad mood, which may influence attention, memory, subjective and physical well-being, etc. Developing effective methods of negative emotion regulation are critical in improving mental health. The study of cognitive appraisal has been the recent focus of this pursuit. Cognitive appraisal is defined as a type of cognitive regulation that may eliminate negative feelings. While much evidence of cognitive appraisal has been reported, the studies often used inappropriate instructions and hence caused a confounding effect due to uncontrollable cognitive activity. For example, some researchers explicitly asked participants to try to reduce their emotional intensity by using reappraisal. As a result, participants would use unnecessary cognitive activities to decrease emotion, leading to the artificial inflation of appraisal effect. In this study, an improved method was used to solve this problem and probe only the function of appraisal on negative emotion. Three pieces of films, the length of which were all about six minutes, were chosen to elicit emotion. According to the emotional valence ratings, one of them was neutral while the other two were negative. Thirty-seven participants for the main experiment were instructed to watch the films with two physiological indexes being recorded: GSR (Galvanic Skin Reflex) and ECG (Electrocardiography). Before and after each film, the participants were asked to rest for four minutes. A rating for their current mood was also made before and after the clips. Different from previous studies, two distinct appraisals were given to two participant groups before the second negative film started, both asked the participants to watch the films naturally. Nineteen of the participants were told the actors’ own stories and emphasized they just performed. The rest, as a control group, were told the content in the film. At the end of the experiment, all participants were asked if they thought the film was fabled when watching the last clip to assess whether the appraisal background influenced their cognition of the film. The results indicated that only GSR and self emotion rating reflected emotional activity differences between the two groups. Analysis of covariance with the GSR level of the first rest as covariant indicated that the GSR level in the actors-appraisal group was lower than that in the control group when watching the second negative film. However, during the first two films, there were no differences between these two groups. On the other hand, analysis of covariance with the self report before the first rest as covariant indicated that the negative experience of actors–appraisal group was lower than that of the control group when watching the second negative film. During the first two films, there were no such differences. The change of GSR and negative experience, as anticipated, indicated that appraisal decreased physiological reaction to negative emotion. To sum up, people with the knowledge that the emotional stimulus was fabled showed more peaceful physiological activity along with lower negative emotion rating. These results indicate the effect of appraisal on emotion.