Abstract: Max Weber demonstrated the great significance of protestant ethics to the development of modern capitalism in Europe.But in Weber’s theory,protestant ethics was an existent idea,and the historical reasons of its occurrence hadn’t been given.This absence on analysis caused Weber’s theory to get away from the historical materialism.In the late medievaltime,with the development of capitalism,the strength of bourgeois gradually became strong.The development’s demand of real economy and science was the deep reason of protestant ethics’s occurrence.