Rational design of high-performance photocatalysts/catalysts is crucial for sustainable development. To achieve this goal, a comprehensive understanding and precise description of structure-performance relationships of photocatalysts/catalysts are highly desirable. While photocatalysis/catalysis involves complex systems and processes, approximate descriptors have been proposed for sorting out simple pictures of complicated structure-performance relationships concerned. In this review, some important descriptors involved in photocatalyst/catalyst design including work function, dipole moment, d-band center, and Fermi softness are reviewed first with special attention being paid to their working mechanisms and applications. Then strategies of tuning photocatalytic/catalytic performance on the basis of these descriptors are outlined. Finally, challenges and opportunities for photocatalyst/catalyst design based on descriptor control are discussed.