Abstract: The research used PPA method to study of allelopathic activities among four species of Lolium multiflorum.Digitaria sanguinalis and Galium tricorne was used as the receiver plants.The results showed that the seeding growth were inhibited obviously by four species of Lolium multiflorum.The powder additives of Maximus′root and mixture of Barmega′s stem and leaf had the strongest effect on Digitaria sanguinalis.The powder additives of Barmega′root and mixture of stem and leaf of Maximus and Jumbo had the strongest effect on Galium tricorne.Among four species, the inhibitory effect of the root powder additive was stronger than the stem and leaf mixture on seeding height of receptor, and the stem and leaf mixture was stronger than the root on root length of receptor.The inhibition rates on seeding height of Galium tricorne were 60.75%and 46.76%respectively when treated 2.0g/L of the root and mixture of stem and leaf powder.The five addition levels of four species had a certain degree of inbibiton on Digitaria sanguinalis and Galium tricorne.The overall trend is that with the increase of adding amount, the inhibition enhanced gradually, especially in three adding levels of 0.50g/L, 0.75g/L and 1.0g/L (P<0.05) .