Chongwenmen Metro station of No.5 line of Beijing Metro crosses underneath the existing Metro line, with the distance between the vault of Chongwenmen Metro station and the soleplate of the existing Metro line being only 1.98m. Piperoofs consisting of huge steel pipes are installed as advance reinforcement. The paper introduces the major technologic measures of the construction of the piperoofs and the ground settlement control methods, analyses the distortion mechanisms of the piperoofs and compares the measured distortion values with the calculated values.