NOVELTY - In-situ method for recovering underground water contaminated by petroleum hydrocarbon by using peat as additional medium, involves pre-treating peat, culturing functional fungi, solidifying the cultured functional fungi on treated wet peat, mixing the peat loaded with functional fungi with crude sand uniformly to obtain reactive barrier supporting medium, and packing the reactive barrier supporting medium in permeable reactive barrier.    USE - In-situ method for recovering underground water contaminated by petroleum hydrocarbon e.g. benzene, toluene, ethylbenzene, xylene and naphthalene.    ADVANTAGE - The method is cost-effective, and does not cause environmental pollution.    DETAILED DESCRIPTION - In-situ method for recovering underground water contaminated by petroleum hydrocarbon by using peat as additional medium, involves (a) suspending soil sample from contaminated site in germfree water, magnetically agitating the soil sample at a high speed for 30 minutes, filtering foreign materials and gravel using eight layers of gauze, allowing the solution to stand for 1 hour, inoculating 50 ml of suspension to 200 ml of enriched culture medium, culturing the suspension at 10 degrees C and 120 rotations/minute for 15 days, inoculating fungal suspension in fresh enriched culture medium, culturing the suspension at 10 degrees C, subculturing the suspension consecutively for 5 times and for 9 days, each time, and reducing the use of carbon source at each time until petroleum hydrocarbon becomes the sole carbon source, (b) inoculating suspension to inorganic salt culture medium using diesel fuel as sole carbon source, culturing the suspension at 10 degrees C, monitoring the increase of fungi and the degradation of diesel fuel, reducing culturing time gradually and accelerating culturing speed until the degrading function of indigenous flora is stable, (c) diluting the selected mixed indigenous flora in different gradients and coating onto an inorganic salt solid plate, culturing the strain at 10 degrees C for 15 days, inoculating individual colonies onto a common solid plate, streaking the individual colonies to obtain pure strain, inoculating the pure strain onto an inclined plane, and preserving the culture medium, where the strain is identified as Yarrowia sp., Rhodococcus sp., Acinetobacter sp., Pseudomonas sp. and Novosphingobium sp., (d) drying peat, crushing the dried peat, sieving the crushed material, treating the powder at 140 degrees C for 3 hours, soaking the peat having a particle size of 0.25-1 mm in purified water for 24 hours to obtain wet peat, (e) drying aquifer sand at the pre-recovered site, sieving and preserving 0.5-2 mm coarse sand, (f) culturing five kinds of functional fungi separated in step (c), inoculating 10% of activated seed solutions to 300 ml of inorganic salt culture medium containing 400 mg/l of diesel fuel, mixing the materials at 10 degrees C at 120 rotations/minute (rpm) for 60 hours to exponential phase with 10000000000 fungi/ml, centrifuging the strain suspension at 8000 rpm for 15 minutes, washing thallus by 20 ml of phosphate buffer, centrifuging the strain suspension at 8000 rpm for 15 minutes, repeating the steps for three times, collecting thallus and preparing them into strain suspension (10000000000 fungi/ml), (g) adding wet peat into a glass container, adding suspension prepared in step (f), culturing functional fungi at 10-12 degrees C for 48 hours, and solidifying the five kinds of functional fungi on peat, (h) mixing the peat fixed with functional fungi with coarse sand in a volume ratio of 1:4 uniformly to obtain reactive wall supporting medium, and (i) packing the reactive wall supporting medium in 30-35 cm wide ditch in layers, and flatting and compacting the medium at every layer to obtain permeable reactive wall.