The invention provides a method and device for detecting the viscosity of a valve, and the method comprises the steps: obtaining a detection valve set, a set value set and a threshold value set of a control loop in a preset time period; obtaining first differential value distribution which is used for representing the distribution conditions of the detection value set and the set value set; obtaining a first factor which is used for representing the nonlinear degree of the first differential value distribution; obtaining second differential value distribution which is used for representing the distribution conditions of differences between all threshold values and a mean value in the threshold value set; obtaining a second factor which is used for representing the approaching degree between the second differential value distribution and mean distribution; and obtaining the viscosity of the valve according to the first factor and the second factor, wherein the viscosity is positively correlated with the first and second factors. The method does not need to carry out ellipse fitting and other complex calculation, and can quickly detect the viscosity of the valve.