The 5th Xi'an International Workshop on Graph Theory and Combinatorics was held online from June 25th to 29th, 2021. The workshop was hosted by Northwestern Polytechnical University, organized by the School of Mathematics and Statistics. The academician Katona, Academician Simonovits of the Hungarian Academy of Sciences and Academician Gutin of the European Academy of Sciences, Professor Weifan Wang,the Chairman of the Graph Theory Combination Branch of China Operations Research Society, and other 36 international well-known experts made online reports. A total of more than 230 experts and scholars from more than 10 countries such as China, Hungary, Netherlands, France, the United Kingdom, Germany, Belgium, Serbia, Australia, Japan and South Korea participated online.