A tunable L-band ring Er3+-doped fiber laser(EDFL) with a temperature control Cu-coated long-period fiber grating(LPFG) is reported.The coated LPFG is used as a band-prevented filter.The resonant wavelength of LPFG can be adjusted by changing its environment temperature using the const-current source.The coated LPFG,which is inserted into the fiber ring cave,will tune the highest gain point of the fiber laser ring.Furthermore the fiber laser wavelength is also tuned.In the temperature range of 20-180 ℃,the optical fiber laser wavelength-tunable range of 20.72 nm(1 560.35-1 581.07 nm)is achieved.The fiber laser′s 3 dB line-width is less than 0.02 nm and the 20 dB line-width is less than 0.06 nm.The side mode suppression ratio(SMSR) is more than 38 dB.Output power stability of laser wavelength is better than 0.02 dBm.Experimental results show that the tunable EDFL has the advantages of easy tunablity,narrow line-width and stable performance.