With the rise of modern rational experimental science, natural science represented by mechanics and biology has made great progress, and at the same time, geology, chemistry and physiology have also made great progress. The outstanding achievements of natural science in the18th century and the early19th century are the establishment of cell theory, the discovery of energy conservation and transformation law and the proposal of biological evolution theory. Empirical natural science has made such remarkable achievements, accumulated a lot of empirical scientific knowledge, and provided a brand-new way of thinking and research methods for social science, thus making it possible to get rid of the traditional pattern of theoretical speculation and qualitative description in the past, broadening the field of vision for observing problems and causing new breakthroughs. The achievements of British classical economics, represented by A Smith and D Ricardo, are examples of social science breakthroughs in this period.