Government attention selectively distributed to various issues in policy-making processes is usually reflected in language, such as metaphors in political discourse. In addition, metaphor change may reveal how conceptualizations of major topics such as economy and ecology evolve over time. After self-building a corpus of China’s 45-year Government Work Reports, this study explores whether there is a difference in attention to topics of economy and ecology over time and investigates the diachronic change of metaphor use on them based on a modified framework for diachronic metaphor change analysis. Results show that attention to economy has been steadily decreasing while attention to ecology has been growing, and that there is an increasing tendency of using more economy and ecology metaphors. Metaphor change on the use of source domains is arranged on a continuum, ranging from constant use (war for economy and ecology, and journey and object for economy), incremental change (living organism and building for economy and ecology, and object for ecology) to fundamental change (building and living organism for ecology). This study may enrich the understanding of diachronic metaphor change by providing a Chinese perspective on the metaphor use in government discourse over time.