The invention relates to plant protein extracting, in particular to a non-degeneration plant holoprotein extracting solution and a preparing method thereof. The extracting solution is characterized by being an aqueous solution containing a phosphate buffer solution, EDTA, glycerol, PVP and protease inhibitors. The extracting solution has the advantages that plant holoprotein extracted with the holoprotein extracting solution is suitable for analyzing the activity of protease and measuring the protein concentration with methods such as BCA; the holoprotein is not degenerated, reducing agents influencing measuring of the BCA and the like are not added, the extracted holoprotein can be stored for several months in the frozen mode, and sediment is basically avoided after re-melting; in addition, the activity of the holoprotein is basically free of influences before and after storage, the extracted holoprotein is high in amount and can be further directly used for further separation purification, and therefore the extracting solution has important application value in the aspect of plant physiology and biochemistry researching.