What herb is use to cure such ailment
First, the western diagnosis of reflux/gerd is not an essential part of how you choose appropriate herbal formulas from a Chinese Medicine perspective. For a general explanation of how diagnoses work in Chinese Medicine (and accordingly how you begin to choose appropriate formulas) please read “What Does Acupuncture Treat?”.
Our Chinese Medicine options for GERD page has some of the more common TCM diagnoses and potentially useful Chinese herbal formulas for that condition. One of the more common diagnoses is liver qi stagnation with spleen qi deficiency and the formula shu gan wan is often used for that condition. In that case, however, any formula from the “regulate and harmonize the liver and the spleen” category could potentially be helpful. But proper treatment, requires proper diagnosis, so you have to have the diagnosis in Chinese Medicine terms first.