Abstract: For improving the process stability of RAT during loosening and conditioning, the control principle of RAT in WQ3315 loosening and conditioning machine was analyzed, the optimization of PID parameters and adjustment of opening threshold of compensation steam valve with field experiment setting were proposed to realize the steady state process control of RAT. The results showed that:1) adjusting and optimizing of PID parameters effectively controlled the stability of RAT. After adjustment, reasonable P value reduced the median value of the peak and valley deviations in RAT curve from 2.5 to 1.5; I value prolonged the fluctuation cycle of RAT from 3 to 8 minutes; and D value flattened the fluctuation curve of RAT to avoid frequent fluctuation; 2) the adjustment of opening threshold of compensation steam valve affected the process control of RAT greatly, the preferable opening threshold of valve was in the range of 6% to 10%.