The invention relates to a biogas slurry concentrate and an engineering preparation method, which belongs to the technical field of biogas slurry resource utilization. The method comprises the following steps: pretreating a membrane of a chicken manure biogas slurry, passing the pretreated biogas slurry through an ultrafilter membrane of an inorganic ceramic membrane for filtering impurity, passing through a nanofiltration membrane and a reverse osmosis membrane for interception and condensation, and final removing solid insoluble particles in the biogas slurry, the macro-molecule substance which is difficult to be absorbed by the crops, high power concentrated biogas slurry organic micromolecule nutrients. The method overcomes of disadvantages of easy membrane obstruction, severe damage, difficult high power condensation, difficult engineering stable operation in prior art, the obtained biogas slurry concentrate finished product is nano level organic state micromolecule substance, has the advantages of comprehensive and balanced nutrition, good water solubility, strong permeability, high activity, and high practical application value.