Abstract: Using iron tailings from Qian’an City, Hebei Province as the substrate, the effect of sludge biochars as amendment on the growth of ryegrass in the short term is studied, aiming to provide a basis for urban sludge resource utilization and soil phytoremediation of iron tailings. Using urban sludge as the main raw material and agricultural waste straw as an additive, biochar is prepared by pyrolysis at different temperatures （300 ℃, 700 ℃） and straw addition amounts （0%, 15%, 30%）. And using biochar as an amendment, mixes with iron tailings sand, and represented by ryegrass, a 60 days pot experiment is conducted to observe the effect of biochar addition on plant growth in iron tailings soil. The results show that at a pyrolysis temperature of 300 ℃, sludge biochar （85SC300） prepared by adding 15% straw and sludge biochar （70SC700） prepared by adding 30% straw at a pyrolysis temperature of 700 ℃ have the best promoting effect on plant growth. The germination rates are 86%, 94%, respectively, which are higher than the 49% in the control group; the plant height increase from 10.52 cm for control group to 25.32 cm and 24.84 cm; the leaf width increase from 4.5 mm to 8.2 mm and 7.2 mm; the biomass increase from 5.21 g to 10.49 g and 9.84 g. The experimental study on the effect of different addition amounts of sludge biochars on the growth of ryegrass is conducted using the above two types of sludge biochar. The results show that with the increase of the amount of sludge biochar, the growth of plant gradually improved until the addition amount is 10%, the germination rates reach 87% and 90%, the plant heights are 27.21 cm and 26.91 cm, the leaf width are 9.0 mm, 8.7 mm, the biomass are 10.85 g, 11.21 g, respectively. Further increase the amount of sludge biochar, the growth of plant is suppressed. In summary, urban sludge can be pyrolyzed to prepare sludge biochar, which can be mixed with iron tailings to improve the growth of plant in iron tailings soil and provide a basis for iron tailings plant remediation.