In order to investigate the effectiveness of Osmose process for the practical treatment of wood this study has been made using water soluble preservatives such as Malenit and chromated zinc chloride. The results obtained in this investigation are as follows: 1. The penetration of Malenit in sapwood has been observed deeper than that of chromated zinc chloride for all species tested in this investigation. 2. The penetration of preservatives applied in soft wood, ie. Pinus densiflora and Larix leptolepis has been observed better results than that of hard wood, i.e., Quercus accutissima and Carpinus laxiflora. 3. The longer stack covering, despite of preservatives applied and size of wood tested, has given better penetration for all species tested, and the fastest diffusion has been occured in 15 days from they day started. Following after 15 days diffusion had gradualy become slower. 4. The length of time needed for effective penetration has taken 45 days for all species tested, reaching twenty millimeters (20mm) in depth in case of Malnit, that means also more than 50% of penetration into sapwood portion. However it has taken 45 days fer Pinus densiflora and Larix leptolepis, reaching fifteen millimeters (15mm) and 60 days for Quercus accutissima and Carpinus laxiflora, reaching same fifteen millimeters in case of chromated zinc chloride, that means also less than 50% (except 50% for Larix) of penetration into sapwood portion. 5. Deeper penetration of preservatives from the wood surface has been observed in the larger wood than the smaller wood for all species tested, although the penetration ratio between the width of sapwood and the length penetrated has been observed smaller in larger wood than smaller wood. 6. The relation between moisture content of wood and the penetration of preservatives into wood tested has shown the linear regression, that is, the more moisture content brought the deeper penetration. 7. Following the result obtained at this investigation osmose process with Malenit applied has indicated as a useable process for the none pressure treatment of wood.