The book takes the effect of Protestant Ethics on the spirit of "rational" capitalism, which proposed by Max Weber in his book "Protestant Ethics and the spirit of capitalism", as the main line, and makes a further comparative analysis and demonstration of the relationship between Protestant Ethics and market economy by setting forth background, historical development, core idea and cultural resource of "rational" capitalism, and comparison with China's market economy and private capital. Meanwhile, by recognizing essential conditions and factors of rational market economy, makes a deeply analysis on the reason why private capital in Chinese history failed for the formation of rational capitalism, and moreover, the gap for private capital in modern China in forming rational market economy.