Based on the Heckscher-Ohlin model,this essay makes a comparison of the changing comparative advantages and structure of trade in services among China,America and India.With the help of time series analysis of the effect of accumulation of factors of production of the three countries on their respective exports in services,it is found that China has a comparative advantage in trade of labor-intensive services.By contrast,America has a comparative advantage in trade in services of human capital-intensive and physical capital-intensive sectors,and India only has a strong comparative advantage in computer and information sector with relatively high human capital-intensity.The above-mentioned conclusion provides a factor-based explanation of the differences of the comparative advantage of trade in services among the three countries,and it is implied that China should make great efforts to develop education and to accelerate the accumulation of human capital to optimize the structure of the service industry which plays an active role in improving the balance of trade in services. <<