This paper aimed to understand the area change and distribution of medium-low yield farmland, and offered basis to the improvement of medium-low cropland and its increase of grain production in Tianjin. Based on the statistical date of Tianjin and its relevant counties and districts, the yield standard was set up to classify high- yield, medium- yield and low- yield cropland in Tianjin. The author analyzed area change of medium-low yield cropland in six agricultural counties and districts (including Jixian County, Wuqing District, Baodi District, Ninghe County, Jinghai County and Dagang of Binghai New Area) from 1980 to 2010. The results showed that the average yield of grain rose from 2445 kg/hm² in 1980 to 5130 kg/hm² in 2010, increasing 109.82%. The area of medium-low yield cropland was reduced from 291 250.13 hm² in 1985 to 76489.87 hm² in 2010, coming down 74% . In Tianjin, the area of medium- low yield farmland of 2010 accounted for 19% of the total cropland, of which the ratios of medium-low yield cropland of Jinghai County, Jixian County, Dagang of Binghai New Area, Wuqing District, Baodi District and Ninghe County were 43.12%, 18.59%, 17.23%, 14.01%, 7.05% and 0, respectively. Low soil nutrient content, drought and water shortage, soil salinization were the main yield limiting factors to medium-low yield cropland in Tianjin in 2010. The countermeasures to improve the medium- low yield cropland were proposed, involving enhancing the investment of the government, strengthening the construction of water conservancy infrastructure, further improving the soil fertility, as well as saline and alkaline land, optimizing the farming system and planting drought and salt tolerance crops, etc.