The accurate measurement of solar absorber coating absorption is of great significance to the evaluation and optimization of the absorber performance. At present

the experimental researches of absorber coating absorption are mostly limited to the flat metal substrate. By taking the cylindrical tube of tower solar molten salt absorber

two widely used measurement methods for testing the absorption of curved surface coatings are proposed. The equipment preparation of Blu-Tack method is simple but the operation is complex

and the equipment preparation of diffuse reflection box method is complex but the operation is simple. The two methods isolate the interference of ambient light during the measurement process

and obtain the measured absorption of various coatings attached to the surface of plate and tube. The fitting curve is then established by the corresponding relationship between the absorption of different coatings on the plate and tube

so as to modify the measured data to obtain the absorption of the absorber tube coating. The results show that

the accuracy of the fitting curve R~2≥0.995

the maximum relative error is 13.39% when the absorption of 2.5 cm diameter tube is measured directly under unshaded conditions

and the relative error reduces to 0.27% and 0.45% by using Blu-Tack method and diffuse reflection box method

respectively. The difference of the relative error of each point of the two methods is less than 0.30%. The greater the coating absorption

the less the influence of each factor on the measurement results. In the test method of Blu-Tack

the larger the tube diameter

the smaller the measured absorption.