Method for prolonging service life of top-bottom composite blowing converter bottom

The invention provides a method for prolonging the service life of a top-bottom composite blowing converter bottom. The method for prolonging the service life of the top-bottom composite blowing converter bottom comprises the following steps of: when melting loss of air permeable bricks at the converter bottom achieves 100-150mm, after steel is discharged completely and converter slags are poured away, adding the following repairing mass into the converter in percentage by mass according to the quantity with the shim thickness of 50-150mm each time: 75-85% of MgO, 7-14% of C, 1-3% of CaO, 1-2% of SiO2, 0.5-1.5% of Fe2O3, and 2-10% of bonding agents, and staying for 2-3 seconds; sintering the repairing mass naturally for 40-70 minutes by utilizing temperature in the converter, then sintering for 60-120 minutes again at 700-1,200 DEG C, and inputting for smelting; repeating the step (1) and the step (2) after smelting for 10-30 converters, and shimming repeatedly in the way until the converter bottom rises by 1