Abstract: The textbook uses the intuition of the number line to represent the point of the rational number a, and obtains the definition of "the distance between the point representing the number a on the general number line and the origin is called the absolute value of the number a". Students can not understand the position, function and function of absolute value concept in rational number set, which is not conducive to teachers’ teaching and students’ learning. The concept of absolute value is actually a device by which the non-rational numbers are transformed into themselves and the rational numbers into their opposite numbers, thus returning the newly established set of rational numbers to the set of non-negative fractions. Any operation established in the set of non-negative fractions can flow unimpeded into the set of rational numbers. This factual conception provides an effective way to understand the teaching and learning of absolute value concept.