The present invention provides a mineral insulated cable assembly, the mineral insulated cable assembly includes cables, wherein the cables adopt inorganic mineral insulated cables, and the mineral insulated cable assembly further comprises: a connector set, wherein the connector set is used for connecting one end of the two cables; a bellows, wherein the bellows is sleeved on an outer circumference of a plurality of the cables, and the bellows is for protecting the cables; and a connector transfer tail attachment, and the connector transfer tail attachment is fixedly connected to the connector set and the bellows. The mineral insulated cable assembly adopts an inorganic design, and enables the cables, the connector, and the transfer tail attachment etc. in the assembly to be free of organic materials, and has no heat aging and irradiation aging mechanism, and can meet very demanding working environment such as high temperature, high pressure, high humidity and high irradiation etc. inside or on edge of a reactor pressure vessel, can meet 60-year working life, and enables the connector to meet 200 insertions and removals.