The authors measured the excavation powers, both in the water and in the air, for such testing materials as sands, gravel, clay, steel balls, small glass balls, and grains made of vinyl by the excavation testing machine which has excavation blade of 6 by 6cm in size, and compared them with the measured records given by the blow interpenetration testing machine, vane testing machine and pushing resitence measuring machine. And we gained the relation between excavation power and grab christaristic of small type grab-bucket. Through excavation test, some uncertain phenomena which are difficult to decide excavation power were found in the records measured by the flow interpenetration testing machine. But the excavation power given by vane testing machine for all model materials coincided well in tedercy with that of records gained by excavation machine. But as for soil and clay, no relation was gained between the measured records given by pushing resistance measuring machine and excavation power by the blade. Distinct relation was found between excavation power and grab charistaristic of grab-bucket for sand, soil and gravel. This was also confirmed by the past technical reports on the dredging grab-bucket written by us.