It is well recognized that the bulk density of coal charge in coke oven is affected by its size and moisture. The degree of such influence on the lower-moistured coal charge (particularly below 5%) has not so far been determined in the pilot coke oven similar to commercial coke oven plant.The Japan Iron and Steel Institute erected equipments for the process that makes, the total coal charge to the briquette, in 1964, with the subsidy appropriated in the same year for the purpose of promoting coal treatment technique. As one of these apparatus was installed to determine the bulk density of coal charged. The Institute, this time, tried to study about the influence of the moisture and size of coal charge on the bulk density, using the large scale apparatus. The test result shows a tendency, approximately similar to those already comfirmed by the laboratory test, with couple of exceptions of rather unexpected results.In handling of dry coal various phenomena, which required our special atten-tion, were observed. The moisture limit of non-dust-generating coal charge is properly regarded as around 6%.