As an optical saturable absorber(SA),single-walled carbon nanotubes(SWCNTs) film has many advantages,including ultrafast recovery time,high nonlinearity,broadband operation,and simplicity of fabrication.Together with its low cost,compatibility with fiber,device flexibility etc.,it has attracted much attention in ultrafast laser field.This paper demonstrates the stable passive mode-locking pulse sequence outputs from the fiber laser using SWCNTs as absorber.Since the polymethylmethacrylate(PMMA) is easy to form film and has good mechanical properties,it can be used as a matrix of SWCNTs.Mixing PMMA with single-walled carbon nanotube powder and dispersing them in the 2-dichlorobenzene solution,we made SWCNTs film on the end face of a single-mode optical fiber by means of optical induction.The SWCNTs/PMMA film is introduced in a ring cavity fiber laser as an optical saturable absorber for passive mode-locking,and a stable pulse sequence is obtained experimentally.The output pulses have the repeated frequency of 8.366 MHz,which is the fundamental frequency of the cavity.The central wavelength is 1 562 nm,and the mode-locking pulse trace is 1.2 ps.