We have conducted VLBA phase-referencing monitoring of H _ { 2 } O masers around the red supergiant , S Persei , for six years . We have fitted maser motions to a simple expanding-shell model with a common annual parallax and stellar proper motion , and obtained the annual parallax as 0.413 \pm 0.017 mas , and the stellar proper motion as ( -0.49 \pm 0.23 mas yr ^ { -1 } , -1.19 \pm 0.20 mas yr ^ { -1 } ) in right ascension and declination , respectively . The obtained annual parallax corresponds to the trigonometric distance of 2.42 ^ { +0.11 } _ { -0.09 } kpc . Assuming the Galactocentric distance of the Sun of 8.5 kpc , the circular rotational velocity of the LSR at the distance of the Sun of 220 km s ^ { -1 } , and a flat Galactic rotation curve , S Persei is suggested to have a non-circular motion deviating from the Galactic circular rotation for 15 km s ^ { -1 } , which is mainly dominated by the anti rotation direction component of 12.9 \pm 2.9 km s ^ { -1 } . This red supergiant is thought to belong to the OB association , Per OB1 , so that this non-circular motion is representative of a motion of the OB association in the Milky Way . This non-circular motion is somewhat larger than that explained by the standard density-wave theory for a spiral galaxy , and is attributed to either a cluster shuffling of the OB association , or to non-linear interactions between non-stationary spiral arms and multi-phase interstellar media . The latter comes from a new view of a spiral arm formation in the Milky Way suggested by recent large N-body/smoothed particle hydrodynamics numerical simulations .