Abstract: A pilot test for large-diameter cluster DTH reverse circulation drilling technology based on the large diameter drilling project in a coal mine was carried out.During the tests，by adopting the Φ710/311mm Reverse circulation cluster DTH and 127/70mm double wall drill-pipe，a good performance of reverse circulation was achieved by optimizing the parameters of reverse circulation such as air volume，air pressure，and rotary speed etc..The highest ROP was 4m/h，and the average ROP was 2.1m/h，which were increased more than 2.6 times as much as that by the conventional cone bit drilling method under the same condition.The pilot test results showed that large diameter cluster DTH reverse circulation drilling technology was an effective drilling technology to solve the problem of hard rock drilling in large diameter hole，and is worthy to be promoted in application.

Key words: DTH, Cluster DTH, Large-diameter DTH, Reverse circulation drilling, DTH drilling