Green manure is an organic fertilizer that is derived from to plow the plants still fresh in the soil while the plant is fully grown or in the flowering period. The most popular green manure crops are the jack bean, cowpea and sunn hemp, etc. The green manure, it consists part of rapid and slow decomposition. Biodegradable part sooner will be the nitrogen source for the plant to grow. Cellulose, hemi-cellulose and lignin are slow to decompose about 20% of the plant material will add organic matter to the soil. Based on previous research, it is found that increasing the organic matter in the soil to make the soil particle dispersion, soil water uptake and soil nutrient uptake is good. However, due to the organic matter, it decomposes faster in tropical climates. It is a source of nutrients in the soil in a short time. It was also found that clay particles were more resistant to degradation than organic matter and could extend the life of the organic matter in soil, thus slowing the decomposition of organic matter. For this reason, the study of the relationship between clay particles and organic matter in soils is important. The study indicated that organic matter after cutting down green manure crop for a period of 15 days was increased. In the 30 days and 45 days, the organic matter content decreased as well as compared to before the experiment. The part of clay particles found that have a lower content compared to before the experiment after cutting down green manure crop for a period of 15 days, 30 days and 45 days, etc. In studying the relationship between organic matter and clay particles are found that organic matter is correlated with quantity of clay particles in a positive direction after the a period of 15 days, 30 days and 45 days. This is probably due to decomposition of organic compounds, causing the clay particle linked compounds “cementing agent” which is the substance that causes the soil particles to adhesive in soil aggregate. As a result, the amount of clay particles increased when organic matter was added to the soil. And also found that the green manure crop decomposition period increase will likely minimize the amount of organic matter in the soil and found that the decrease in the quantity of clay soil particles tend to rise during 15 days and 30 days. But during 45 days found that will likely decrease, etc..