Cultured human fetal lung Fbs was first used to study the relationship between wound age and the change of cFn synthesized by Fbs in Vitro. A sterilized injector was applied to scrap the cultured confluent Fbs and a "wound" was obtained. Fbs around the wound was seen to change from a stationary stage to an active stage. Using the method of immunochemistry and image analysis system (IAS), cFn synthesized by Fbs around the wound was observed at once, 30 min, 1 h, 3 h and 6 h after injury. It was found that cFn began to change 1 h after injury and increased continually within 6 h. It suggests that the change of cFn synthesized by Fbs is time-dependent after injury and this approach breaks a new path in the study on estimation of wound age.