Abstract: Described here in the paper is how to use the 37Mn5 steel to produce the ZT640 economical heavy/mediumwalled seamless steel tube for geological drilling service,involving the manufacturing process,the key control techniques and the quality status,and the control measures as taken to prevent the quench-caused crack of the 37Mn5 heavy/medium-walled seamless steel tube.It is regarded via the analysis that the ZT640 quench and tempered heavy/mediumwalled seamless steel tube for geological drilling service as produced by means of the process of“Converter+LF+Square CC+Round rolling+PQFpipe-rolling+Quenching & tempering”hasall of itstechnical indexes and dimensional tolerances fully conform to applicable technical requirements,which means that the manufacturing process as employed is quite practical.And it is finally concluded that substituting the 37Mn5 steel for the 35CrMo steel is able to bring about the economical production of the said product.