The invention discloses a burner, and a bottom cup comprises a gas inlet passage and a single nozzle which is communicated with the gas inlet passage and arranged upwards. An annular flamethrower is arranged on the bottom cup and comprises a single Venturi tube which is arranged opposite to the single nozzle, a gap is formed between the flamethrower and the bottom cup, and primary air is allowed to enter the Venturi tube from the gap and mixed with gas which is injected from the nozzle to the Venturi tube to form mixed gas. An inner ring mix chamber, an outer ring mix chamber and a middle passage are formed in the flamethrower, the outer ring mix chamber is arranged around the inner ring mix chamber, the middle passage is communicated with the inner ring mix chamber and the outer ring mix chamber, and the inner ring mix chamber is connected with the Venturi tube. A burner cap is arranged on the flamethrower and covers the inner ring mix chamber, the outer ring mix chamber and the middle passage. The burner reduces the cost brought by arranging multiple Venturi chambers in the manufacturing process. The invention further discloses a gas application.