Abstract: In order to make full use of the packed iron tailings, iron tailings, cement, straw and pH regulator were used to prepare planting material sprayed on the slope of the exposed rock. Based on the influencing factors of the cement content and pH regulator dosage, this research aims to study the change law of the unconfined compressive strength with the change of its age. The results showed that, when the cement content is 6%, the strength of planting material can meet the engineering requirement. With the pH regulator dosage increases, the unconfined compressive strength reduces. When 6% and 8% of pH regulator dosage and cement added into the planting material respectively, the unconfined compressive strength increases quickly in 14d.