Taking 278 nurses as samples, with questionnaire survey, this paper explores the formatting mechanism of organizational silence from the perspective of social exchange. Empirical results verifies that perceived organizational support(POS) has a negative effect on acquiescent silence and disregardful silence, leadermember exchange(LMX) also has such effect on acquiescent silence. Trust to origination partly mediates the influence of POS on acquiescent silence, and completely mediates that of POS on disregardful silence; while trust to leader completely mediates the effect of LMX on acquiescent silence. The findings enriches the existing theories of organizational silence, and provides theoretical support for the intervention of organizational silence.