Abstract: Soilless substrate culture can not only save land resources,but also help to solve the problem that diseases and insect pests in traditional soil culture are easy to be invaded by P.macrophyllus.And it can accurately and quantitatively control water and fertilizer,which is conducive to large-scale factory cultivation.Five kinds of compound soilless media made up of perlite,coconut chaff and peat according to different volume proportion were used as culture medium,and traditional garden soil culture was used as control,the physical and chemical properties of different compound substrates and their effects on the seedling growth of P.macrophyllus seedlings were analyzed,and the strong seedling index of P.macrophyllus seedlings were analyzed by multiple regr ession analysis and path analysis,according to the results of the analysis,the formula of the preliminary screening was optimized,the results showed that the optimized matrix formula D1（perlite∶coconut chaff∶peat=5∶4∶3） was superior to the optimized matrix formula C1（perlite∶coconut chaff∶peat=4∶4∶3） and the traditional soil formula Aeration porosity,pH value,soluble salt concentration and available phosphorus concentration were the main factors affecting the index,and the direct path coefficient of aeration porosity to the index reached 1.041,the effect of other factors on the index of strong seedlings is negative,therefore,appropriately increasing the aeration porosity of the composite substrate and decreasing the concentration of acid-base,soluble salt and available phosphorus are beneficial to the growth of seedlings of P.macrophyllus seedlings,it can be widely used as an excellent substrate formula for the cultivation of P.macrophyllus seedlings.