TITLE: GCN CIRCULAR NUMBER: 17651 SUBJECT: GRB 150120B: GMG observation DATE: 15/03/29 08:21:35 GMT FROM: Jirong Mao at Yunnan Obs J. Mao, J. Zhang, and J.-M. Bai (YNAO) report: We observed the field of GRB 150120B (D'Elia et al., GCN 17314) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatory. Observations began from UT 13:42:43.5 20th, Jan., 2015 (about 6.3 hours after the trigger). We clearly detected the optical counterpart with brightness of R=22.1+/-0.1 mag. J. Mao apologizes for this very late GCN circular submission.