Abstract: Based on the social support theory, the influence of social support on old people's psychological health is analyzed to build a mediator model of hope and loneliness for exploring the internal mechanism of the old people's psychological health development. The questionnaire method is adopted to survey 553 old people and the data are analyzed according to the structural equation model. The main results are as follows. First, social support, hope and loneliness are all vital factors in the old people's psychological health. Second, social support predicts hope and psychological health significantly positively but predicts loneliness significantly negatively. Third, the mediating effect of social support on psychological health via the hope is obvious. Fourth, the mediating effect of social support on psychological health via loneliness is obvious, too. Finally, hope and loneliness function as multiple agents between social support and psychological health. The psychological mechanism of social support influencing the old people's psychological health and the mediating effect of the hope and loneliness are verified. Some practical suggestions are given for improving the old people's psychological health.