The temporal evolution of entropy of Jiuzhaigou ecot-ourism areal system has been quantitatively analyzed by using equation of system entropy V = k ln M-k ln C.The computed entropy for Jiuzhaigou ecotourism areal system for 20 years indicates a negative value during 1986-1996, which implies that the system had remained a healthy state during this period. The system entropy value, however, showed a constant increase since 1996 until it turned to be positive in 2000 when the system became cha-otic. After 2000 the entropy value declined until 2003 when it escalated once again. By analyzing the causes and process of en-tropy change of the system, it is argued that fluctuation of entropy value is due to the overloading of tourist service capacity by tourism activities. It is desired to curb the flow of tourist volume and reinforce conservation efforts as well as, so that an ideal balance between conservation and development could be maintained. The temporal evolution of entropy of Jiuzhaigou ecot-ourism areal system has been quantitatively analyzed by using equation of system entropy V = k ln Mk ln C. The computed entropy for Jiuzhaigou ecotourism areal system for 20 years indicates a negative value during 1986-1996, which implies that the system had remained a healthy state during this period. The system entropy value, however, showed a constant increase since 1996 until it turned to be positive in 2000 when the system became cha-otic. After 2000 the entropy value stopped until 2003 when it escalated once again. By analyzing the causes and process of en-tropy change of the system, it is argued that fluctuation of entropy value is due to the overloading of tourist service capacity by tourism activities. It is desired to curb the flow of tourist volume and reinforce conservation efforts as well as so that an ideal balance between conservation and development could be maintained.