政治信任感攸關人民對於權威當局的政治支持，而大學生為社會未來之中堅份子，其政治信任感如何受到大眾傳播媒介的影響，實值得關注。本文以定群追蹤資料，從媒介政治資訊的角度，討論政治信任感的持續與變遷。研究發現，大學生的政治信任感在四波調查研究之間約有四成維持穩定，另外約有六成則不斷變動。至於影響的因素，本文發現大學生對媒介公正性評估愈高，政治信任感則會隨之提升，符合「良性循環論」。再者，當大學生為泛綠認同者，暴露程度高且認為媒介公正時，其政治信任感比起暴露程度低者更低，符合「媒介抑鬱論」。 Political trust among the general public determines citizens' support to the political system. College students are the future elites of the society and therefore how their sense of political trust is shaped by the mass media deserves close examination. This article analyzes the continuity and change of college students' political trust in Taiwan from the viewpoint of political communication of mass media based on a four-wave panel study. We find that from year to year about 40% of our respondents remain stab le in their political trust while about 60% of them change all the time. Two determinants are most significant. One is the subjective evaluation of the fairness of the mass media report, i.e., the more they feel media coverage is fair, the stronger sense of political trust they have. This finding fits the "virtuous circle theory." The other key factor is party identification, i.e., the pan-green identifiers who expose more to the media or believe that the media coverage is fair tend to have lower political trust than those low exposure. This finding fits the "media malaise theory."