The effect of flow compression on the determination of laminar flame speeds utilizing spherical bombs at normal and high pressures is studied theoretically and numerically. The results show that compression induced flow has significant impacts on the accuracy of the measured flame speeds. An analytical expression for compression induced flow is obtained, and by considering the compression induced flow, the compression corrected flame speed (CCFS) is proposed for flame speed measurements using expanding spherical flames. The theoretical results are validated by direct numerical simulations of outwardly propagating spherical CH4/air flames using detailed chemistry. It is found that the accuracy of the measured flame speeds is greatly improved by using the CCFS and the pressure range is increased by considering compression effect.