Interlayer story teaching method is a foreign language teaching method developed by Professor Ji Yuhua of Xiamen University, which tells stories in the way of mother tongue and foreign language. For example, in the story "Three Little Pigs and the Big Wolf", there is such a "sandwich" text: "The first little pig built a house with straw and felt very safe. But the second little pig felt that the straw house built by the first little pig was not strong enough, and decided to find wood and build a stronger wooden house. " The name of this teaching method is taken from the sandwich (also called sandwich) in western food, that is, two pieces of bread (usually triangular) with fast food made of meat, eggs or cheese in the middle.

Sandwich story teaching method is a transitional method, which is like a bridge, so that children can reach the other shore happily and safely without going through all kinds of hardships, even risking their lives to wade or swim across the river. (Ji, 2000) No matter at home or abroad, the sandwich story teaching method has a common cause, that is, the contradiction between the interesting content of foreign language textbooks and the poor foreign language level of beginners cannot be solved. Beginners can't understand the original foreign language materials that meet students' interests and cognitive development level, while those simple texts written to take care of students' foreign language (low) level make students feel ridiculous, bored and even stupid. The research of educational psychology shows that if the intelligibility of listening and reading materials is too low (that is, the difficulty is too high) or the readability is too low, students will lose their inner motivation. This kind of risk, especially children's education, cannot be taken. Therefore, the design and construction of "sandwich bridge" is a strategic project for children's foreign language education in China.