Kim then graduated in 1983 and obtained his MS degree from Seoul National University.

Kim's Ph.D. thesis was supervised by Alfred K. Mann and resulted in real-time and directional measurement of solar neutrinos in the Kamiokande-II detector and search for short-time variation.

He jointly led the efforts of discovering the top quark in 1994 and measuring its mass in 1995 using the Fermilab Tevatron hadron collider as a member of the CDF collaboration.

The observation and mass measurement of the particle opened a new field of "top quark physics".

He shared the Asahi Prize in 1999 with Super-Kamiokande collaboration for the observation of atmospheric neutrino oscillation.