The objective of the study was to investigate the effect of addition of chlorella (CA) on the change of nutritive values, organic acids and microbes on mixture of whole crop barley and crimson clover (WCB-CC) silage. This study was conducted at the experimental field of National Institute of Animal Science, Cheonan, Korea and consisted of three groups, such as control without CA, with 0.25% CA and with 0.5% CA. The contents of crude protein, total digestible nutrient, and in vitro dry matter digestibility of WCB-CC silage were increased by CA treatment (p<0.05). However, acid detergent fiber and neutral detergent fiber of WCB-CC silage were low compared to control (p<0.05). The pH of WCB-CC silage in CA treatment showed no significant difference, but the content of lactic acid and the number of lactic acid bacteria in CA treatment significantly increased as compared to control (p<0.05). These results suggest that the addition of CA could improve the quality of WCB-CC silage