Gold catalysis is considered one of the most important breakthroughs in organic synthesis during the past decade, but a rational understanding of ligand effects in gold catalysis is lacking. Most gold-catalyzed reactions go through three major stages: (i) electronic activation of alkyne (or allene) to generate a vinyl gold intermediate; (ii) protodeauration to generate the product and regenerate the cationic gold catalyst; (iii) decay of the active gold catalyst. Our research provides a clearer understanding of how ligands influence each of the three stages in the gold catalytic cycle. What is even more important, by not focusing on a particular gold-catalyzed reaction, we have been able to categorize most gold-catalyzed reactions and propose a ligand design protocol for each category of gold-catalyzed reactions.