A converter bottom blowing system comprises a first gas source connected in parallel with a lime powder silo, a lime powder blowing tank and a first injector, where a first cut-off valve is arranged between the lime powder blowing tank and the first injector; a second gas source connected in parallel with the biochar powder silo, the biochar powder blowing tank and the second injector, where a second cut-off valve is arranged between the biochar powder blowing tank and the second injector; a converter, where a plurality of bottom blowing lances are arrayed at a bottom of a converter, the bottom blowing lances are connected with the first injector and the second injector through a three-way valve, a third cut-off valve is arranged between the first injector and the three-way valve, and a fourth cut-off valve is arranged between the second injector and the three-way valve.