Based on the bamboo texts of the early Western Han dynasty excavated at Zhangjiashan, this thesis investigates the evolution of Han characters by tracing the origin of form mélange of radicals and components in Han characters. In this thesis, “mélange” refers to the phenomenon of miswriting characters and radicals of different forms, pronunciations and meanings, or components of irrelevant forms and meanings as those of the same form, without limiting to the mélange of characters of similar forms. First, the author set the prototypes of different sets of mixed radicals or components in the Zhangjiashan Han Bamboo Texts in order to restore their original appearances. Then, the author traced if the writing of particular mixed radicals or components are found in the survived bronzeware script of the Western Zhou dynasty and the Spring and Autumn Period, the characters of the six countries in the Warring Period or the characters of the Qin dynasty. The author also examined the influence on form mélange of the “clerical script transformation” where “contours” were transformed into “strokes” in Han characters, to elucidate the radical or component mélange of the Zhangjiashan Han Bamboo Texts.