Abstract: Cassirer's early epistemological thought is confined to the theoretical framework of Kantian philosophy and neo-Kantianism,taking "scientific facts" as the starting point and the final point of cognitive criticism.Through the reconstruction and sublation of Kant's construction technique of "critique of reason",Cassirer's epistemology has undergone the evolution from the epistemology of "genetic" to the epistemology of "symbol".He regarded myth,language and science as different forms of symbol created by human activities,and proposed that all conceptual understanding must be based on the mythological world at the most primitive level,which is highlighted in natural language and ended in theoretical science.Thus,Cassirer not only extended the field of epistemology to the fields of humanities,but more importantly promoted the level of cognitive reflection and found a new foundation and starting point for it.This is a revision of his early epistemological thought,and it is also the most essential difference between Cassirer's Philosophy of Symbolic Forms and traditional Kant and Neo-Kantianism.The turn of Cassirer's epistemology is a major breakthrough in philosophical epistemology after Kant.Cassirer integrates natural science and humanities with "symbol",grasps rationality and explores human nature from the view of human culture as a whole.The high tolerance and openness of Cassirer's philosophy has opened up a broader way for modern Western philosophy to get out of the theoretical dilemma.

Key words: Ernst Cassirer, epistemology, philosophy of symbolic form, Neo-Kantianism, transcendental logic, symbolic form