The invention discloses a biological improvement method of sand degraded soil. The method combines humic acid and microorganism bacteria agent to prepare soil restoring agent. The soil restoring agentis covered on ditches and used in sand degraded soil with liquorice after the beginning of spring and before summer; the field management should be done for 1 year to 2 years. The invention can rapidly increase the content of organic matter in soil and increase types and quantity of microbe in the soil; thus the invention improves the ecological environment of soil and achieves the purpose of improving the sand degraded soil.