Abstract: Comparatively analyzed are the effects by the immersion inner water spray quenching process and the outer-showering and inner-spray quenching process on the microstructure and properties of the 110 37Mn5 heavy-walled steel pipe. It is regarded via the analysis that increasing the contents of Mn and Cr of the pipe up to 1.5% and 0.25%respectively,and adopting the outer-showering and inner-spray process will reduce the bend of the pipe,and improve its property stability.Relevant production practice shows that thanks to the outer-showering and inner-spray quenching process,the 37Mn5 steel pipe has its reticular ferrite disappeared,and its austenite fully transformed into the martensite,and after tempered,the pipe has homogeneous and dense tempered sorbite microstructure,and possesses all the mechanical properties as satisfying the requirements specified under relevant technical agreement.