Taking domestic violence cases as an example, using experiments to explore the influential mechanism of victims' emotional state and injury degree on their credibility. Results showed that in domestic violence cases, the credibility of sad victims is significantly higher than that of calm victims, and the credibility of seriously injured victims is significantly higher than that of slightly injured victims; The victim's sadness is in line with the observer's expectations of his role as a victim, leading to sympathy for them, which can enhance their credibility. In judicial practice, the victims' sadness should be rationally evaluated, we should not only respect the victims' right to express sadness, but also avoid its possible adverse impact on the realization of litigation value.