In order to predict coal and gas outburst, biological contrary degree algorithm is proposed based on contrary degree and biological theory and prior values and posterior values. In the nature, there are prior data and posterior data; such as positive words and negative words. According to the contrary matrix, the testing data can be predicted based on the testing data by using biological contrary degree algorithm. Meanwhile, the accuracy of biological contrary degree algorithm is 100%. The results show that new algorithm is feasible and effective