The invention provides an ecological method for restoring polycyclic aromatic hydrocarbon polluted farmland soil, which comprises the following steps: selecting plants such as corns, soybean, castor-oil plants and alfalfa with the restoring function of the polycyclic aromatic hydrocarbon polluted soil for seeding according to a plant conventional mode, wherein the plant growth period is one growth season and is between 100 and 150 days; 2, applying efficient biological microbial agents to farmland at 5 to 10 days before the plant seeding with the application amount between 40 to 50 kg/mu, and carrying out ploughed fallow on the farmland in 24 hours after the application; 3, applying sludge fermentation fertilizer into the farmland at 2 to 3 days before the plant seeding with the application amount of 100 to 200 kg/mu, and carrying out ploughed fallow and ridge preparation on the land in 24 hours after the application; and 4, installing a water discharge pump used for water discharge in a rain reason in the restoring field every 4 to 5 ridges of the land, and carrying out ploughed fallow for 2 to 3 times in each month of the three months before the plant growth. The invention has the characteristics of low cost, strong operability, no secondary pollution and high restoring efficiency.