The invention discloses a large-displacement single-pipe layered polymer injection adjustable device. The large-displacement single-pipe layered polymer injection adjustable device comprises a measurement and adjustment tool guide-in mechanism, an injection amount adjustment mechanism and a polymer depressurization and viscosity-keeping mechanism. The measurement and adjustment tool guide-in mechanism has a guide function and a positioning function. The injection amount adjustment mechanism has the functions of spirally lifting and dropping an injection allocation core and adjusting the injection amount of the polymer depressurization and viscosity-keeping mechanism. The polymer depressurization and viscosity-keeping mechanism is provided with a spindle injection allocation runner with the depressurization and viscosity-keeping characteristics. The injection allocation core has an enough inner drift diameter to guarantee the conduction of work like profile test. Meanwhile, a bridge type passage is arranged in a layered polymer injection measurement and adjustment work barrel, and polymer injection of other layers is not affected when the current layer is tested. The large-displacement single-pipe layered polymer injection adjustable device has the characteristics of large injection amount, good viscosity-keeping performance and adjustable injection amount, realizes single-pipe layered polymer injection measurement and adjustment multi-layer injection, resolves the existing difficulties of layered polymer injection of offshore oil fields, and can effectively improve the utilization rate of polymers and the oil displacement effect.