Hong's music has been described as "a work of iridescent freshness" (BBC Music Magazine), "the sound is utterly luminous" (Fanfare Magazine), and "the harmonies and fluid dynamics were modern" (The New York Times).

Her compositions include works for solo instruments, orchestra, chorus, ballet, and electroacoustic media with special interest on timbre and pre-determined pitch structures. In 2022 she has been awarded a Guggenheim Fellowship and a Charles Ives Fellowship from the American Academy of Arts and Letters. Also in 2022, she was elected as an Associate by the Royal Academy of Music (ARAM) upon its 200th anniversary. Hong has received commissions from the Fromm Music Foundation, the National Flute Association, Texas Flute Society, the MATA Festival, Lorelei Ensemble, iSing Silicon Valley, the Tongyeoung International Music Festival, Kumho Asiana Cultural Foundation, and the Seoul Philharmonic Orchestra, among many others.

Her Missa Lumen de Lumine on the ECM New Series (ECM 1929), performed by the vocal ensemble Trio Mediaeval, received critical acclaim and reached the top ten on the Billboard Classical Chart and iTunes classics. Sungji has received 54 distinctions for her compositions, including the Kazimierz Serocki (1st Prize), the Franz Josef Reinl-Stiftung (1st Prize), Magistralia (1st Prize), Ilshin Composition Prize (1st Prize), In Nova Musica Competition (1st Prize), Jesus Villa Rojo (1st Prize), European Competition of the State Conservatory of Thessaloniki (1st Prize), Temple Music Composition Prize (1st Prize), Crwth Competition (1st Prize), the international competition for original ballet music at the ISCM World Music Days – Slovenia (1st Prize), Montserrat International Camera Music Composition Competition (1st Prize), Theodore Front Prize (IAWM), Yoshiro Irino Memorial Prize (ACL), and Christian Fellowship of Art Music Composers Scholarship.

Hong holds degrees from the Hanyang University, the Royal Academy of Music, and the University of York in the United Kingdom and is an Assistant Professor of Music Composition at the University of North Texas.