The invention discloses a boiler slagging condition monitoring method based on the outlet temperature of a combustion chamber. The monitoring method includes the steps of 1, detecting the outlet temperature of the combustion chamber; 2, calculating the temperature change before and after soot blowing and the temperature rising rate after soot blowing of an outlet of the combustion chamber according to detection in the step 1; and 3, judging that combusted coal tends to form slag when the temperature change is greater than 50 DEG C and the temperature rising rate is greater than 5 DEG/h, and judging that the combusted coal is not suitable for long-term combustion and adjusting the coal type when the temperature change is greater than 80 DEG C and the temperature rising rate is greater than 10 DEG/h. The invention further provides a boiler slagging condition controlling method based on the outlet temperature of the combustion chamber. According to the monitoring method and the controlling method, scientific use of a soot blower can be effectively guided, the outlet temperature of the combustion chamber can be continuously recorded, the temperature change before and after soot blowing and the temperature rising rate after soot blowing of the combustion chamber can be calculated, the use time of the soot blower can be further obtained, and the cleanliness degree of a water-cooled wall and the slagging characteristics of the coal type can be reflected.