HD 149277 is a rare SB2 system with a slowly rotating magnetic He-rich primary with P _ { rot } = 25.4 d. The CFHT/ESPaDOnS archive spectra revealed P _ { orb } = 11.5192 \pm 0.0005 d indicating strong subsynchronous rotation of the primary component . Such a strong subsynchronous rotation was not detected in any other SB2 system with a magnetic chemically peculiar component . Our inspection of the spectra revealed the presence of resolved Zeeman split spectral lines allowing us to determine the variability of the mean magnetic field modulus over the rotation period . The maximum of the magnetic field modulus concides roughly with the positive extremum of the longitudinal field , whereas the minimum of the modulus with the negative extremum of the longitudinal field . No evidence for a longitudinal magnetic field was seen in the circularly polarized spectra of the secondary component . Using archival data from the ASAS3 survey , we find in the frequency spectrum only one significant peak , corresponding to the period P _ { phot } = 25.390 \pm 0.014 d. This value is in good agreements with the previous determination of the rotation period , P _ { rot } = 25.380 \pm 0.007 d , which was based on longitudinal magnetic field measurements .