Population distribution, habits and characteristics of Galinsoga quadriradiata was investigated in this project. Based on the results, appropriate control methods would be carried out for preventing the expansion of G. quadriradiata population, and maintain local biodiversity in Miaoli. The results showed that G. quadriradiata were found in 7 townships among all 18 townships. They could flower all year round and produce more flowers in cool season than those in hot season. Not yet become a threat to cultivation area. There were two type of controlling methods, chemical and non-chemical method. Overall, we suggested mechanical removing method before cooling season would have better performance in protecting local ecological environment.