Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO2 conditions (8-20 MPa). Temperature evaluated from C-2 Swan bands (d (3)Pi(g)-> a (3)Pi(u)) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p (5) P-3,P-2,P-1 -> 3s (5) S-2(0)) of hf plasma under sc CO2 conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.