Gross Domestic Product (GDP), reflecting the production capacity of acountry or a specific area within a particular time period, is an important economic statistic. The current official estimation of the GDP of Taiwan covers only the post-1951 period. As a first step toward understanding thelong-run economic growth of Taiwan, this paper provides an estimation of Taiwan's GDP from 1910 to 1950. Our estimates show that Taiwan's pre World War II GDP had a larger fluctuations than that of the post-War period. Further more, the post-War GDP growth rates in general were higher than that of the pre-War period. The discrepancy in the growth rates was more apparent in the secondary and tertiary sector. How to explain the disparities of fluctuations and growth rates of the real product across different sectors and time periods is a challenging work for future research projects.