Nowadays, many organizations will let many customers inject a large amount of hyaluronic acid in a certain area in order to make profits. If the amount of injection is too large it will swell, compress the local muscles and reduce movement. And if the local area is too full and swollen it can lead to a particularly unnatural expression. The stiffness of expression caused by hyaluronic acid injection is mainly related to the excessive amount of injection or local damage to the nerves. It is recommended that patients choose a standardized institution, use reasonable medication and inject at reasonable levels to avoid the stiffness of the face. It is not easy to have a stiff face when filling after hyaluronic acid injection, but it is easy to have a stiff face with botulinum toxin injection. Because this method has to control the movement of muscles, the expression will look stiff. Hyaluronic acid injection is filling capacity and usually does not affect the movement of muscles.