Abstract: The study aims to find out the incidence of ‘black walnut’ in different site conditions which can decrease the yield and quality in Shanyang County Shangluo City, and the reasons led to ‘black walnut’. The author selected the mountain area, shallow mountain area and plain area as 3 test fields in a walnut plantation. In each test field, 10-15 years old fruiting walnut trees were chosen stochastically. The author observed the temperature, humidity, the rate of insect fruit and the reasons leading healthy fruit to ‘black walnut’. The results showed that the ‘black walnut’ outbreak degree had a direct relationship with different site conditions. The incidence of the ‘black walnut’ in plain area was slightly smaller than that in the shallow mountains, and the maximum incidence of the ‘black walnut’ was found in the remote mountains. The reason of ‘black walnut’ in the remote mountains was black spot, followed by Atrijuglans hetauhei Yang, but the situation in the shallow mountains and the plain area were just the opposite. The results of this investigation could be a guidance to control the disease Xanthomonas juglandis Dowsen and the insect pest Atrijuglans hetauhei Yang.