NOVELTY - A fixed microballoon is of circular ball shape with a gap. The diameter of the microballoon is 2.5-3 mm. The fixed microballoon granule comprises sodium alginate as embedding material, solid calcium carbonate as pore former and slow releasing agent, and attapulgite as the absorbing agent. Petroleum hydrocarbon degrading bacterium and nutrient element are absorbed.    USE - A fixed microballoon for repairing petroleum polluted soil, preferably for degrading petroleum hydrocarbon in soil (claimed).    ADVANTAGE - The fixed microballoon is featured with nutrition, protecting function, slow releasing, activity, high stability, good transmission, and convenient use.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an application method for fixed microballoon containing calcium carbonate for repairing petroleum polluted soil, comprising culturing and preparing bacteria suspending liquid of petroleum hydrocarbon degrading bacteria; and uniformly mixing sodium alginate and attapulgite in deionized water and sterilizing at high temperature in humid and heat condition. The condition is maintained at 40-60 degrees C. The solid sodium alginate is poured into the mixture of sodium alginate-attapulgite and mixed uniformly. The temperature is maintained at 40-60 degrees C to obtain sodium alginate -attapulgite-calcium carbonate gel. The bacteria liquid is added into the gel liquid and mixed. The petroleum hydrocarbon degrading bacteria is at 0.001-0.004, preferably 0.002 g/ml. The sodium alginate is at 0.01-0.06, preferably 0.03 g/ml. The attapulgite is at 0.005-0.03, preferably 0.01 g/ml. The solid calcium carbonate is at 0.01-0.1, preferably 0.05 g/ml. The mixture is dripped into the calcium chloride solution to obtain spherical granule. The calcium chloride is at 0.02-0.08, preferably 0.02 g/ml. Ball is formed by the spherical granule for 5-30 minutes. The spherical granules are placed into the diluted hydrochloric acid to act until there is no obvious bubble. They are added into the calcium chloride solution, soaked, and cleaned. The granules are moved into the propagating culture medium, cultured, and cleaned to obtain the fixed microballoon.