YTQC type string magnetic is one of the auxiliary tools to ensure normal drilling operation and bottom hole cleaning after downhole accident treatment. The main feature of this product is that it works together with the junk mill in the fishing operation, which is different from the previous practice of lifting the drill after milling, and then connecting the drill string with the strong magnetic fishing device to go down the well for bottom hole cleaning, saving a trip down the well, which saves both drilling costs and fishing time.