Abstract: 【Objective】 Northeast China is the main grain production base in China, which has been significantly affected by climate change in recently. It is of great significance to understand the impact of normal and extreme climate states changes on crop yield in Northeast China for regional crop production and national food security. 【Method】In this study, we analyzed the effects of normal and extreme climate states changes on maize yield in 81 counties in Northeast China from 1980 to 2018 by the main climatic factors. 【Result】 (1) The average temperature, growing degree-days (GDD), and heat degree-days (HDD) during the maize growth period showed an increasing trend, and the rising rates were 0.34 ℃·(10a)^-1℃/10a, 47.07 ℃·d·(10a)^-1/10a, and 5.14 ℃·d·(10a)^-1/10a, respectively. Precipitation showed a decreasing trend, with the rate of 7.0 mm·(10a)^-1/10a; the average temperature, GDD, and HDD increased from northeast to southwest, and precipitation showed an increased from northwest to southeast. (2) The meteorological yield of maize in Northeast China showed an increasing trend from 1980 to 1999, with a rate of 80.93 kg·hm^-?2·a^-1/a, while it showed a decreasing trend of 46.25 kg·hm^?-2·a^-1/a from 2000 to 2018. In terms of spatial distribution, it showed an increasing trend from the middle to the surrounding areas. The area with high yield was concentrated in the eastern part of Heilongjiang. Liaoning was the most stable change, the fluctuation range was stabled in the middle area. (3) By the multiple linear regression model, HDD contributed the most to meteorological yield from 1980 to 2018, and the effect was negative, which meant extreme high temperature had the greatest impact on maize yield in Northeast China and caused maize yield reduction; GDD had a positive effect and indicated the average temperature increased maize yield, and the greater GDD, the more yield increased; precipitation had a negative effect; the interaction between temperature and precipitation had a positive impact on maize yield in Northeast China. 【Conclusion】 Normal and extreme climate states changes and its impact on maize meteorological yield in Northeast China from 1980 to 2018 are as follow: the normal and extreme temperature showed an overall increasing trend, and the normal precipitation showed a decreasing trend. Extreme high temperatures and normal precipitation led to a decrease in maize yield, but the average temperature increases maize yield, and the extreme high temperature had the greatest impact. In the future, it is necessary to make full use of the average temperature state and minimize the harm caused by extreme high temperature to ensure a high-stable maize production. 

Key words: climate change, northeast China, maize yield, contribution rate