Abstract: Xinji No.1 coal mine have a lot of coal resource and the quality is good.Predicting the water inflow is important to exploit the coal resource.Introduction the coal mine flood water basic source and the change of the water inflow.Took advantage of the every month water inflow statistical data from 1999 to 2011 and the Markov chain prediction theory,and then divided into 5 intervals of the water inflow to predict the probability of January 2012.The result is equal to the actual situation.This way needs a large number of statistical data.