Rare earth elements (REEs) and their composites could promote the growth of agricultural products, which, hence, have been widely used in farms as an important trace fertilizer, especially in China. In this work, two kinds of rare earth organic complex europium-salicylic acid-[1,10-phenanthroline] (Eu(Sal)(3)Phen) and praseodymium-salicylic acid-[1,10-phenanthroline] (Pr(Sal)(3)Phen) were synthesized first. Then we prepared the Eu,Pr(Sal)(3)Phen/LLDPE composites by adding Eu(Sal)(3)Phen and Pr(Sal)(3)Phen (with a weight ratio of Eu(Sal)(3)Phen: Pr(Sal)(3)Phen = 1:1) into the linear low-density polyethylene (LLDPE) matrix by mechanical mixing. The experiments of fluorescent properties showed that the composites can absorb ultraviolet light (UV) (wavelength range of 200-400 nm) and can emit red-orange light (wavelength range of 600-680 nm), which is necessary light source for growth crop. The fluorescent properties of Eu,Pr(Sal)(3)Phen treated for different time at 160 degrees C and treated for 10 min at different temperatures have been tested. It has been found that the fluorescent intensity of the Eu,Pr(Sal)(3)Phen reduced with the increase of treated time and treated temperature. Furthermore, the fluorescent properties of Eu,Pr(Sal)(3)Phen/LLDPE composites placed at room temperature for different time have been analyzed. It has been proved that the decrease in the fluorescent intensity of the Eu,Pr(Sal)(3)Phen/LLDPE composites is not evident within 3 months. Therefore, these composites meet the requirements of growth crop in one quarter, sufficiently.