Abstract: Abstract: Poly-γ-glutamic acid (γ-PGA) is a natural and water-soluble polymer, which consisted of D-glutamic acid and L-glutamic acid monomer linked by amide bonds between the α-amino and the γ-carboxylic acid functional groups, and γ-PGA is easily biodegradable and its degradation products are nontoxic in the environment. Main ingredients of γ-PGA are made of protein, minerals and vitamins, and its appearance is white powder. Moreover, γ-PGA has strong water absorption property, which may be able to store water from rainfall and irrigation for enhancing crop growth. In recent years, it is the fact that γ-PGA is being increasingly used in Agriculture because the enhancement of people's environmental awareness and the requirements of national sustainable development strategy play an important role in application of environmental protection material. An experiment based on the vertical one-dimensional infiltration soil column was conducted to investigate the effect of γ-PGA on soil water infiltration and its water holding characteristics. The soil in the experiment was collected from Changwu Agro-ecological Experiment Station (35°12′ N, 107°40′ E) in Xi'an, China. The soil passed through a 2 mm sieve, and was dried under normal temperature conditions. The particle size of soil was measured with Mastersizer 2000, and its soil texture was silty loam (3.47% clay, 92.26% silt and 4.27% sand). The soil was mixed with the γ-PGA with different contents (0, 0.5%, 1%, 2% and 4%) respectively. Then, the mixed soil was packed into organic glass column (46 cm in length, 5 cm in diameter) with 5 cm each layer till a depth of 40 cm. The Mariotte lucite was used to provide a free water supply with 1.5 cm in depth on the surface of chamber. The experiment started when the Mariotte lucite was opened. In order to make the head stable, the filter paper was laid at the soil surface. The results indicated that the cumulative infiltration volume, infiltration rate and wetting front reduced from 15.94 to 6.7 cm, from 0.0193 to 0.0089 cm/min and from 38.1 to 15.4 cm respectively with the increase of the content of γ-PGA after 500 min. The infiltration coefficient in Kostiakov formula reduced from 0.808 to 0.538, and the infiltration index increased from 0.53 to 0.623. The infiltration rate in Philip formula reduced from 0.704 to 0.292 cm/min0.5. Saturated hydraulic conductivity in the Green-Ampt formula and effective soil water diffusion rate in humid area reduced from 0.0043 to 0.0011 cm/min and from 1.19 to 0.16 cm2/min respectively, and soil moisture suction had not obvious trend of change with the increase of γ-PGA content. Saturated hydraulic conductivity in the formula of vertical one-dimensional infiltration reduced from 0.0044 to 0.001 cm/min, while the changes of distribution coefficient and comprehensive shape coefficient were not obvious with the increasing of γ-PGA content. Moreover, saturated soil moisture content increased from 0.4725 to 0.5408 cm3/cm3 with γ-PGA content increasing. With γ-PGA content increasing, the water contents of the treatments were significantly increased in the 0-10 cm soil layer compared to the controls. But the change of water content of the treatments in the 10-40 cm soil layer was contrary to that in the 0-10 cm soil layer. The results suggest that γ-PGA can not only enhance effectively soil water holding capacity, but change obviously soil moisture distribution patterns in soil profile and decrease soil infiltration capacity effectively. In conclusion, the application of γ-PGA can make more water accumulate in the root zone of crops to promote plant growth, and improve water use efficiency. The study may provide valuable theoretical basis for the application of γ-PGA in water-saving agriculture and soil improvement.