Objective:To explore the effects of mild cognitive impairment (MCI) on perceived facial trustworthiness for older adults.Methods:From May to June 2019, 30 young subjects (young group) were recruited, and 30 young older adults (young elderly group), 30 middle older adults (middle elderly group), and 30 elderly (elderly group) with normal cognition were recruited. At the same time, 30 older adults with normal cognition (cognitive normal elderly group) and 30 older adults with MCI (MCI elderly group) were recruited. All subjects were scored on the trustworthiness of young and elderly faces.SPSS 26.0 software was used to conduct a multivariate analysis of variance on the data to explore the differences in perceived facial trustworthiness among elderly people of different ages and elderly people with different cognitive function.Results:(1) A comparison of the facial trustworthiness scores of young and elderly faces among the young group, young elderly group, middle elderly group, and elderly group showed that, interaction between face age and age was significant ( F(3, 116)=6.30, P=0.001), the main effect of face age was significant ( F(1, 116)=23.18, P<0.001), and the main effect of age group was significant ( F(3, 116)=11.88, P<0.001). Simple effect analysis showed that the facial trustworthiness scores of elderly faces in the young elderly group (5.02±0.85), middle elderly group (5.15±0.55), and the elderly group (4.87±1.03) were higher than that in the young group (3.74±0.71), and with a statistically significant difference (all P<0.001). There were no significant differences in the facial trustworthiness scores of elderly faces among the young elderly group, middle elderly group, and elderly group (all P>0.05). There were no statistically significant differences in the facial trustworthiness scores of young face among different age groups ( P>0.05). (2)The comparison of facial trustworthiness scores among the young group, cognitive normal elderly group, and the MCI elderly group showed that, the interaction between face age and cognition was significant ( F(2, 87)=8.33, P<0.001), the main effect of face age was significant ( F(1, 87)=5.97, P<0.01), and the main effect of cognition was significant( F(2, 87)=39.37, P<0.001). Simple effect analysis showed that the facial trustworthiness scores of elderly faces in cognitive normal elderly group was higher than those in the young group and the MCI elderly group( P<0.001). There were no significant differences in the facial trustworthiness scores of elderly faces among young group and the MCI elderly group ( P=0.191). The facial trustworthiness scores of young faces in cognitively normal elderly group and young group were higher than those in the MCI elderly group( P<0.05). There was no statistically significant difference in the facial trustworthiness scores of young faces between cognitively normal elderly group and young group ( P=0.134). Conclusion:There is a positive effect on the perceived facial trustworthiness in older adults with normal cognition, but there is no positive effect on the perceived facial trustworthiness in the older adults with MCI. Cognitive decline affects perceived facial trustworthiness in the elderly.