This study was conducted to find an optimal combination rate of castor meal for the good qualitative compost and to estimate the humification grade by physico-chemical characterization and phyto-toxicity test during composting of the mixture with cow manure and castor meal. The material ratios of the compost which was mixed with cow manure(C), castor meal(C), and saw dust(S) were 5 : 1 : 4(CCS-1), 5 : 2.5 : 2.5(CCS-2) and 5 : 4 : 1(CCS-3) by volume to volume, and they were decomposed for 60 days. In the result, the changes of temperature in all treatments during composting radically increased more than $63.6^{circ}C$ at the incipient stage, and gradually decreased around $42^{circ}C$. At the 60 days after the treatment, pH was slowly increased from 7.0 to 8.0, and the C/N ratio was 12.3~13.8 at the final composting stage. The low C/N ratio value was caused by the castor meal with high nitrogen level(T-N 5.7%). G.I.(germination index) showed in the range of 77.5 to 82.6 in all treatments. Among all treatments CCS-1 was appeared to be the best condition for composting. Therefore, the combination rate of castor meal which was used for compost humification improvement could be recommended 10% to manufacture the good qualitative cow manure compost.