To provide a fluorinated ether composition useful for surface treatment to impart water/oil repellency to the surface of a substrate, a method for producing the fluorinated ether composition, and a coating liquid containing the fluorinated ether composition, as well as a substrate having a surface-treated layer, and a method for producing the same. Said composition comprises at least two fluorinated ether compounds which are represented by A-O-Q-(CbF2bO)d—X—O—B10 and which are different in B10. X is a divalent organic group having no CF2O. B10 is —CH2CH2CH2SiLmRn, —CH2CH(SiLmRn)CH3, —CH2CH═CH2 or —CH═CHCH3. A is a perfluoroalkyl group or group B10. Of the total of group B10 in said composition, the proportion of —CH2CH2CH2SiLmRn is from 90 to 99 mol %, and the proportion of —CH═CHCH3 is from 1 to 10 mol %. L is a hydrolyzable group, and R is a monovalent hydrocarbon group. b is an integer of from 1 to 10, and d is an integer of from 1 to 200.