A random laser is a unique system in which an assembly of disordered scatters is distributed all over the gain medium to sustain the required optical feedbacks by multiple scatterings for the stimulation of lasing action. Due to the absence of well-defined resonance cavity or rigid alignment of optical elements, it is hence difficult to control the random lasing emissions. In this study, we experimentally demonstrated a flexible random laser fabricated on the polyethylene terephthalate (PET) substrate with a high degree of tunability in lasing emissions. Random lasing wavelength is blue-shifted monolithically with the increasing of bending strains exerted on the PET substrate, and the maximum shift of lasing wavelength of ~15 nm was achieved as a 50% bending strain is exerted on the PET substrate. Such observation is highly repeatable and reversible, and it validates that we are able to control the lasing wavelengths by simply bending the flexible substrate. The result herein shows a great advance for the applications of flexible optoelectronic devices, including wearable devices, ultrathin display, and health sensors.