The invention discloses a full decontamination waste gas recovering flexible pressurization system comprising a diesel engine. The diesel engine is provided with a gas inlet pipe and a gas exhaust pipe, the gas inlet pipe is connected with a gas compressor, the gas exhaust pipe is connected with a turbine generator, and the turbine generator is connected with a decontamination heat exchanging device through a pipeline. The decontamination heat exchanging device comprises a heat exchanging box body communicated with the turbine generator through the pipeline, a water chamber is arranged in the heat exchanging box body, a steam storage chamber is arranged above the water chamber, a superheater is arranged between the water chamber and the steam storage chamber, one end of the superheater is communicated with the water chamber, and the other end of the superheater is communicated with the steam storage chamber. A synchronous valve is arranged on a steam transferring pipe, and the gas exhaust end of a steam turbine is connected with a condenser. A composite heat exchanger, a reduction heat exchanger and an oxidation heat exchanger which are connected in series are arranged in the water chamber, the gas inlet end of the composite heat exchanger is communicated with the heat exchanging box body, and the gas outlet end of the oxidation heat exchanger is communicated with a desulfurizing device. With the adoption of the full decontamination waste gas recovering flexible pressurization system, the power of the diesel engine is increased, and the oil consumption rate is reduced.