The invention relates to a preparation method of a prefabricated magnesium oxide porcelain column mineral insulated cable, and solves the shortcomings in the prior art. The technical scheme comprisesthe following steps: step 1, pretreating a copper strip, a copper rod and a porcelain column respectively; step 2, taking out the magnesium oxide porcelain column to perform filling; step 3, the copper strip is put out by a strip retractor and then wiped and cleaned, the copper strip is finely cut by a copper strip precision cutting machine, the trimmed and wound copper strip is sent to a precision wheel type longitudinal wrap forming machine for longitudinal wrap forming and the longitudinal wrap formed copper strip is continuously longitudinally seam-welded by a longitudinal seam welder under the protection of argon gas or helium gas; step 4, after each roll of the copper strip is used up, butting is carried out by a welding machine under the protection of argon gas or helium gas and thewelding part is polished and leveled; step 5, head forming, stretching and annealing of the filled and welded cable are performed with a disc drawing machine to stretch out the magnesium oxide mineral insulated cable meeting the requirements; and step 6, performing water immersion packaging after take-up and pay-off.