Large thrust ratio, long-working micro-ablation throat insert and throat structure of expansion section

The invention discloses a large thrust ratio, long-working micro-ablation throat insert and a throat structure of an expansion section. The throat structure comprises a throat insert, a backing, a bottom lining and a thermal insulation blanket of the expansion section; the external surface of the throat insert matches with a first step surface of the backing; the bottom of the backing is plastered on a second step surface of a bottom lining; the thermal insulation blanket of the expansion section matches with a third step surface of the bottom lining; the second step surface and the third step surface are on the same level; at the same time, the backing and the thermal insulation blanket of the expansion section are plastered in a circumference direction. Compared with prior art, the advantages and beneficial effects are that large thrust ratio and long-working are satisfied; the throat assembly has the characteristics of micro-ablation; a good heat insulation effect in long working time is realized; i