Abstract: In order to solve the difficult problems of the gas content frequently over limit caused by the borehole spouting occurred during the construction process of the pre-drainage borehole through beds drilling in the driving strip of the high gassy mine,a new intergrated device with the gas,water and dust separator and the dus t collection was researched and developed. With the improvement on the sleeve sealing performance of the gas dust collector,the size of the gas dust collector and the volume of the gas,water and dust separator were enlarged and the structure of the conventional gas and dust separator was optimized. A comparison test was conducte d on the gas concentration variation and the gas content over limit condition in the air returning side of the borehole drilling field when the new device and the conventio nal gas and dust separator were applied. The results showed that in comparison with the conventional gas and dust separator,when the new type gas,water and dust se parator installed during the drilling period of the pre-drainage borehole through beds,the gas concentration at air returning side of the drilling field would be highly reduc ed and the gas volume fraction would be reduced individually by 37%and 95% when the borehole drilled through No. 8 seam and No. 7 seam in Datong No.1 Mine. The numbers of gas content over limit was obviously reduced from ten times per month to two times per month.