A study on the structure-activty relationship between (Z)-hexadec-9-enal (Z-9-16:Ald) and its analog was conducted by comparing the structures of the sex pheromone of cotton bollworm, Helicoverpa armigera (Hübner) with its fluorinated analog using computer molecular fitting. It is demonstrated that the structure of analog substituting for hydrogen atom on the terminal carbon atom is similar to Z-9-16:Ald. The EAG result showed that there is no significant difference in activities between Z-9-16:Ald and its fluorinated analog synthesized.