This article provides an overview of gas turbine blade tip external cooling technologies. It is not the intention to comprehensively review all the publications from past to present. Instead, selected reports, which represent the most recent progress in tip cooling technology in open publications, are reviewed. The cooling performance on flat tip and squealer tip blades from reports are compared and discussed. As a generation conclusion, tip clearance dimension and coolant flow rate are found as the most important factors that significant influence the blade tip thermal performance was well as the over tip leakage (OTL) flow aerodynamics. However, some controversial trends are reported by different researchers, which could be attributed to various reasons. One of the causes of this disagreement between different reports is the lacking of unified parametric definition. Therefore, a more appropriate formula of blowing ratio definition has been proposed for comparison across different studies. The last part of the article is an outlook of the new techniques that are promising for future tip cooling research. As a new trend, the implementation of artificial intelligence techniques, such as genetic algorithm and neural network, have become more popular in tip cooling optimization, and they will bring significantly changes to the future turbine tip cooling development.