Abstract: The paper aims to study the influence of meteorological factors on maple leaves’ turning red and forecast maple leaves viewing index. Using 3 meteorological observation stations (Benxin, Benxinxian, Huanren) meteorological data and 65 monitoring samples in 16 monitoring areas (Guanmenshan park, Laobiangou scenic area, Chinese maple leaf road, maple valley and so on) maple leaf phenological data from September to October in 2014-2017, we analyzed the meteorological conditions affecting the discoloration of maple leaves and the characteristics of the best viewing period. Results indicate: (1) the average time of entering the first red state in Liaodong mountain area is on September 26, and the average time of entering the positive red state is October 8th. Maple leaves becomes the red states in the early first frost day significantly ahead of time corresponding to the first frost day period in which the spot red state is good, there are more than 70% of the samples becoming red state 1 day prior to 1 day after the first frost day. (2) The effect of temperature on maple leaf discoloration is remarkable, and the lower the average temperature, highest temperature and lowest temperature, the higher the color changing rate of maple leaves grows in the beginning of the coloring of maple leaf. Precipitation has a certain effect on the discoloration of maple leaves. In the years with more rainfall in July and September, the maple leaves enters the best viewing late state, but the viewing period of maple leaves was longer. (3) After September 16, maple leaf enters the beginning of the red state when the daily averaged temperature is 12-18 ℃, the red state when the averaged daily temperature is 5-15 ℃, and the early red state when the daily minimum temperature is below 10 ℃, and accumulated more than 3 d, the red state when the daily minimum temperature is lower than 6 ℃, and accumulated more than 3d, turning red when the range of daily temperature is greater than 15 ℃, and accumulated more than 3 d.(4) There is an obvious cooling before the maple leaves enters the initial red state. The initial red state will appear in the 1std or 2nd after cooling, and the spot red state will appear in the 3rd or 4thd after the cooling.(5) According to the analysis result, the fenghong meteorological index was established, being divided into four levels, which represent suitable, suitable, unsuitable and unsuitable. The level connotation corresponds to the degree of maple viewing, which falls from the first to the fourth grade. Key words: maple leaf rate; correlation analysis; meteorological conditions threshold; maple weather index; additive method of factors