A mode-locked thulium ytterbium co-doped fiber laser(TYDFL) is proposed and demonstrated by using a commercial graphene oxide(GO) paper as saturabie absorber(SA).The GO paper is sandwiched between two fiber ferrules and incorporates a ring laser cavity to generate sohton pulse train operating at 1942.0nm at a threshold multimode pump power as low as 1.8 W.The mode-locked TYDFL has a repetition rate of 22.32 MHz and the calculated pulse width of 1.1 ns.Even though the SA has a low damage threshold,the easy fabrication of GO paper should promote its potential application in ultrafast photonics. A mode-locked thulium ytterbium co-doped fiber laser (TYDFL) is proposed and demonstrated by using a commercial graphene oxide (GO) paper as saturabie absorber (SA). GO paper is sandwiched between two fiber ferrules and incorporates a ring laser cavity to generate sohton pulse train operating at 1942.0 nm at a threshold multimode pump power as low as 1.8 W. The mode-locked TYDFL has a repetition rate of 22.32 MHz and the calculated pulse width of 1.1 ns.Even though the SA has a low damage threshold, the easy fabrication of GO paper should promote its potential application in ultrafast photonics.