Abstract: Poplar is one of the dominant trees which developed very quickly in China in recent years. It is important to study annual dynamics of macro-element contents in order to improve the ability of poplar plantation nutrient management. Annual dynamics of macro-element contents of clone 1-69 and clone I-72 were studied. Results indicated that the value and the annual dynamics of N, P, K, Ca and Mg in different biological components of two poplar clones were similar. Among these components, annual variations of nutrient contents in leaves were the most obvious, and its variation value was 82.6% for N, 82.2% for P, 84.7% for K, 85.7 % for Ca, and 88.7% for Mg respectively. The rule of macro-element accumulated in one-year-old and two-year-old branch was similar, dilute effects of nutrient content existed during the eugenic period of various biological components; among various biological components, mean contents of N, P, K of leaves were maximal and mean contents of Ca, Mg of one-year-old xylems were maximal. The results would provide primary data for nutrient management and productivity maintenance of poplar plantation.