We experimentally investigate a stable freestanding whispering gallery mode (WGM) microlaser based on polymer microdisk formed by a ~500 µm diameter microfiber knot. A quality factor of about 14 700 and a relatively low lasing threshold with about 38.0 µJ/pulse are demonstrated in this structure. When a polymer microdisk is pumped by a 532 nm wavelength pulse laser, WGM lasing with a free spectral range (FSR) of 0.15 nm is observed from the polymer microdisk laser. This work provides a convenient and efficient approach to achieving a WGM microlaser based on a polymer microdisk and collecting the output light.