Abstract: Pressure in earth chamber can′ t be built up in time during conventional launching of EPB shield since it needs to manually remove the retaining structure of steel reinforced concrete in advance. Even though water stopping and reinforcement are carried out at the tunnel entrance, but the problems of soil mass collapse, water inflow and sand gushing can′ t be thoroughly solved. In view of this a calculation model of earth chamber pressure during nonbarrier launching of EPB shield was established by building retaining structure of fiber glass reinforced concrete at tunnel portal, and a formula to calculate earth chamber pressure during non-barrier launching of EPB shield was presented. The application of this calculation model to Beijing metro line 16 shows the calculation model can reflect the build-up process of earth chamber pressure, and the volume of added material like soil and so on before launching is a key factor related to build-up of earth chamber pressure