Abstract: Plant growing Medium Spraying technique (PMS engineering technique)is one of vegetation restoration technologies on the rocky slopes,while PGM is a hard-to-solve core technique.Through the systematic study on dynamic changing rule of PGM in the PMS engineering project,the paper aims to perfect PMS technique,PGM confect and production theory,and to offer scientific guidance and reference to PMS engineering technology.The analytical results of PGM dynamic changing rule show that :PGM chemical constituents regularly change with construction period,and initially it always drops down rapidly,and then the drop degree tends to gentle or even increase in the later stage,and the general content can meet growth needs of plants.Therefore,it can be divided into three periods :medium-spraying technique period,soil material transition period and soil developing period.Meanwhile,it takes PGM content in plant's second growing year as the appraisal index for PMS engineering technique.