Ma's primary research interests are in theoretical cosmology and astrophysics. Among the topics she has studied include the properties of dark matter and dark energy, the cosmic microwave background, gravitational lensing, galaxy formation and evolution, supermassive black holes, and the large-scale structure of the universe. She occasionally manages to climb out of the dark and lumpy universe; during these sunny moments (or rather, moonless nights), she has enjoyed collaborations with observers in studying properties of galaxies using telescopes at Palomar and Keck.