Provided is an air supply device of combined blowing converter bottom relating to steelmaking technology, particularly a bottom-blown air supply device of steelmaking converter, the utility model provides a bottom-blown air supply device of steelmaking converter which comprises a air supply tail pipe and a air supply steel pipe, the air supply tail pipe is connected with the air supply steel pipe by a metal hose, the utility model also comprises at least a bearing plate which is permanently connected with the air supply tail pipe and the air supply steel pipe, the bearing plate is provided with a hole and divided into two half-hole plates to fasten the air supply tail pipe in the bearing plate hole, the two half-hole plates are point welded on the bottom steel plate of the converter, the utility model greatly decreases impact of high-frequency vibration for air brick, lessens or avoids capillary opening plug of air brick and highly prolongs lifetime of air brick.