O. Santolík is active in physics of plasmas and in spacecraft data analysis and interpretation with a focus on plasma waves and related processes. Recent research topics include both linear and nonlinear wave emissions in space plasmas of the ionosphere and magnetosphere of the Earth, ionospheres and magnetospheres of planets of the Solar System, and interactions of waves and instabilities with plasma medium and energetic particles. He is the author or co-author of 300 scientific articles in refereed journals with 8200 citations and with an h-index of 47.

O. Santolík is a member of international teams of currently operating spacecraft missions of ESA and NASA and he also leads instrument development efforts of new scientific spacecraft projects. In 2014 he obtained the Praemium Academiae award from the Czech Academy of Sciences. In 2017 he was elected Vice President of the Union Radio-Scientifique Internationale (URSI) and in 2017-2021 he served as Vice President of Science Council of the Czech Academy of Sciences.