The invention provides an igniter, an ignition device and an ignition method. The igniter comprises an igniter body, a heating unit, a first conduct piece, a second conduct piece and insulation heat conduct pieces. A first chamber is formed in the igniter body, the heating unit is arranged in the first chamber, a first annulus is formed between the heating unit and the igniter body, and the heating unit is electrically connected with the igniter body. A second chamber is formed in the first conduct piece and the first conduct piece is connected with the igniter body. The second conduct piece is arranged in the second chamber, a second annulus is formed between the second conduct piece and the first conduct piece, and the second conduct piece is connected with the heating unit. The insulation heat conduct pieces are arranged in the first annulus and the second annulus. The igniter, the ignition device and the ignition method can be applied in horizontal well sections, the in-situ combustion process and the ignition process are not limited by the length of the horizontal well sections, and also the ignition is even, the ignition length is larger, and the ignition chamber growth is stable.