Abstract: Addressing the alarming and abnormal withdrawing phenomenon of the right-side main milling head of the steel tube edge-milling machine,an analysis is made,involving such aspects as hydraulic movement process,the principle of the hydraulic system and various monitored pressure curves,etc.As a result it is confirmed that the hydraulic cylinder and valves are free of any abnormality,and has nothing to do with the said problem of the machine. Accordingly countermeasures are taken,including screening the electrical alarms,monitoring key electrical signals,deploying temporary power supply,and replacing modules of the DP communication sites,etc. It is finally identified that it is the alarming from the communication remote site that causes loss of the lubrication signal of the right-side No.2 main milling head,and thus in turn causes blackout of the said main milling head. Consequently the said abnormal blackout activates the automatic hydraulic protection function of the said main milling head. Furthermore the hydraulic circuit pressure curve as monitored verifies that the above mentioned abnormal withdrawing movement of the main milling head is caused by the alarming from the remote communication site.