The invention discloses a method for preparing a freeze-drying crisp fruit and vegetable piece, which includes the following steps: blanching raw materials for killing enzyme; preparing a color protection liquid using citric acid concentration, sodium isoascorbate concentration, or cysteine hydrochloride concentration, sodium phytate concentration and embedding medium, wherein, the ratio between the color protection liquid and the slice liquid material is 0.25-1:1; slowly freezing fruit paste with 4-7 mm thickness below a eutectic point at minus 30 DEG C. for one hour; placing the fruit paste on a separator plate of a vacuum lyophilizer after the machine is precooled to a cold trap minus 50 DEG C. with 30 Pa vacuum degree and 40 DEG C. separator plate temperature; heating and drying by programs, wherein, 3-5 DEG C. rises every hour when the temperature is below 10 DEG C.; keeping temperature at 10 DEG C. for 1 hour; heating continuously for rising 5-7 DEG C. every hour; keeping temperature for 2 hours at 40 DEG C.; obtaining the crisp fruit and vegetable pieces with water content below 7% after refrigeration; slicing and packing products in an independent drying room with air humidity 40-50%. The invention has a distinct fruit and vegetable original flavour with larger market prospect.