Abstract: GDP is a key indicator for measuring the size of a country’s economy and the world economic pattern, but there is no consensus on the international comparison method of GDP in theory and practice. This article explains the three main methods of GDP international comparison and their respective characteristics and limitations. It is believed that the essential difference lies in the selection of conversion factors. Based on this, the relative trend of GDP changes between China and the United States from 1990 to 2020 is analyzed from the perspectives of total quantity and industry structure. Research has found that China’s GDP is rapidly catching up with the United States. In manufacturing, in particular, China has significantly surpassed the United States. However, there are significant differences in the relative changes measured by different methods. The exchange rate method is relatively simple in calculation, but is greatly affected by factors such as exchange rate fluctuations; The purchasing power parity method is relatively reasonable in principle, but weak in operability and comparability; The substitution method is relatively reliable in terms of data, but its theoretical basis and objectivity are weak. This study deepens the understanding of the theoretical essence of GDP international comparison methods, calculates the relative trends in the total and structure of GDP between China and the United States, and provides reference for further improving GDP international comparison methods.

Key words: gross domestic product, international comparison, purchasing power parity, economic growth, GDP