Abstract: There are a large number of engineering accidents in the application of traditional rectangular tunnel caused by stability problems which hindered the application and popularization of rectangular tunnel in stoping. In order to improve the stability of rectangular tunnel, this article puts forward a new type of rectangular form which named the rectangle cross section with fillet.This kind of section form using a quarter fillet to replace the traditional rectangular tunnel's four right angles. The finite element software ANSYS is used for the numerical simulation to compare with the traditional rectangular tunnels with the fillet section of displacement and stress, and study the stability of the rectangle tunnel with fillets. The research showed that rectangular tunnel radial displacement decreased, the stress concentration decreased, the overall stability increased after the improving of fillets.