The utilization of farmland drainage water has been concerned by many scholars as an effective way to alleviate the shortage of fresh water resource and reduce the negative impact of the environment. Therefore, we need to understand the variation law of farmland drainage quality and quantity before the utilization.The experiment was carried out to monitor the displacement, mineralization degree, Na+, Cl- concentration and analyze the change rule by sampling the drainage of South Tarim Drain in the Alar Irrigation District for two years. The results showed that the drainage quantity of South Tarim Drain is rich and the monthly variation law is obviously. The total drainage of 2015 was 75 million cubic metres and 2016was 69 million cubic metres. The drainage is salt water all year round. The average TDS in two years is 8.7 g/L and TDS variation law is negatively correlated with the change of drainage quantity. The Variation law of salinity is obviously and positively correlated with the change of drainage quantity. The drainage discharged 0.119 million tons of salt to Tarim river in two years, and the quality types of drainage is Na-Cl. The major cation is Na+, of which the average percentage is 16.7% and the average concentration is 1.4 g/L. The major anion is Cl-, of which the average percentage is 35.6%and the average concentration is 3.1 g/L. It is suggested that for farmland drainage utilize of south Xinjiang, when the drainage quantity is large and the TDS, Cl- and Na+ is less, we could give priority to reuse the drainage.