Abstract: After studying the make and properties of MMH mud series and doing experimerts with them in laboratory,the author and others carried on practical drilling test using MMH mud in Panji coal mine,Huainan and get success.The strata for drilling test are deeply water-sensitive and the rocks are rich of montmorillonite.in the test,the clay layers were drilled through without casing.Thus it was reduced in costs of drilling and increased in economic benefits.