The morphology and microstructure of catkins or flower cluster of poplar/willow were studied comparing with cotton/natural silk by the means of stered microscope, scanning electron microscope(SEM) and total reflection (ATR) spectra (FTIR), respectively. The experimental results showed that the morphology of cotton/silk fiber was thicker and had excellent tensile performance, while poplar catkin fiber was shorter with,less tensile properties. The FTIR analysis showed that the main chemical compositions of cotton and poplar catkins were cellulose and the stretching vibration absorption peak of hydroxyl(—OH) groups in hydrogen bond network of cotton fiber was significantly stronger than poplar catkin fiber.This may explain why the tensile properties of cotton fiber length, fiber flocculant is superior to the catkins of poplar and willow.Silk fiber is different from plant fiber,such as,cotton,poplar catkin) whose main structure is amide structure. Their microstructure difference determines the different properties and applications.