The invention belongs to the technical field of molecular biology, and relates to a method for extracting a high molecular weight genome DNA from an environmental sample. The method of the invention comprises steps of embedding, wall breaking, digestion, electrophoresis, gel recovery and dissolving. An environmental sample is suspended by a fluid suspension, added with low melting point agarose and cooled at room temperature for solidification; a gel block is put in a wall breaking buffer, incubated, and kept vibrating horizontally; the wall breaking buffer is discharged, and a digestion buffer is added to the gel block, incubated, and kept vibrating horizontally; the digestion buffer is discharged, and the gel block is washed by a washing liquid and then washed by an electrophoretic buffer; after wall breaking and digestion, the gel block is cut into small blocks and inserted into a sample application hole of the low melting point agarose gel; gap of the sample application hole is sealed by the low melting point agarose gel, and an electrophoresis is carried out in an electrophoretic buffer; the gel containing DNA is cut off after dyeing, and the DNA is recovered through an electroelution; and the DNA obtained after the electroelution is dried and dissolved in an aseptic deionized water or a TE solution, and a dissolving solution is the extracted DNA. The method of the invention has good repeatability, and operations are simple, so as to completely satisfy molecular operations of database establish, etc.