In the past few decades, metal and metal oxide nanocrystals, as the most common catalytic materials, have attracted broad attention from worldwide scientists. Although considerable progress has been made in nanocatalysis, especially in controllable synthesis of nanocrystalline catalysts, it still remains a great challenge to fully understand the relationship between the catalytic properties (activity, selectivity, and durability) of nanocrystals with their structural characteristics in varied types of reactions. Actually, recognizing the regularity of nanocatalysis and revealing its physical and chemical nature are significant basic issues in catalytic science and technology. According to these basic scientific issues, our group has carried out systematic research work. This mini account highlights the recent progress in this area in our group.