The invention discloses a module used for installing an ejection unit for the tail gas treatment of a diesel engine, wherein the module comprises a gas inlet pipe, a reducer pipe, a gas outlet perforated pipe, a catalytic converter and the ejection unit, and is characterized in that the gas inlet pipe is connected with a pipe body of a small pipe diameter segment of the reducer pipe in a sealing way; the diameter of the reducer pipe gradually increases via a reducer surface, and the inclined surface of the reducer pipe is provided with an ejection unit installation hole; one end of the gas outlet perforated pipe is connected with a pipe body of a large pipe diameter segment of the reducer pipe in a sealing way; and the other end of the gas outlet perforated pipe extends into the catalyst converter. The module has the effects that the airflow distribution effect is good, the noise elimination performance is excellent, and the installation module can be used for installing the ejection units for the tail gas treatment of the diesel engines with different structures.