The invention discloses a preparation method of a saffron decoction piece. The preparation method comprises the following steps of drying: saffron raw materials are flatly paved in a metal container, the metal container is heated by water vapor generated by water bath for drying, and uninterrupted turning is performed to obtain a semi-finished product 1, wherein the temperature of the water bath is 60 to 80 DEG C; humidification: the semi-finished product 1 is flatly paved in a containing tool with holes in the bottom, and the water vapor generated by the water bath humidifies the semi-finished product 1 through the holes, so that a semi-finished product 2 is obtained, wherein the water bath temperature is 85 to 88 DEG C; secondary drying: the semi-finished product 2 is flatly paved in the metal container, the metal container is heated by the water vapor generated by the water bath for drying, and uninterrupted turning is performed, wherein the water bath temperature is 60 to 80 DEG C. The contents of effective ingredients of crocin I and crocin II in the prepared saffron decoction piece are high; the appearance of the obtained saffron decoction piece is attractive; the consumption requirements on the saffron decoction piece in the market are met.