Nowadays, many graphic researchers are interested in 3D outdoor environment. They want to express more realistic natural background with natural phenomenon because computer hardware has become more powerful and increased a demand for a background of 3D natural environment in a content. Especially, e-sports contents and simulation contents with outdoor environment need more natural environment for a background than indoor contents. It is very important technology for a quality of 3D outdoor contents. We propose a software EMtool(Environment Making Tool) for authoring of natural environment for realistic contents. EMtool has been developed to depict relationship and interaction between natural phenomena and include methods for creating natural environment and natural objects. The proposed results are applied to real-time 3D contents such as 3D golf games and simulations for natural objects.