On the one hand, in the primary school stage, the new standard puts forward the learning task of "exploring laws", which is actually the primary stage of function learning; On the other hand, in the junior high school mathematics curriculum, the definition of function only adopts the relatively intuitive "variable theory": the change of one variable causes the change of another variable, but does not adopt the abstract "mapping theory"; At the same time, it does not systematically mention the three elements of function, monotonicity and parity of function and other basic characteristics; Instead, it only requires combining specific functions, effectively infiltrating and gradually revealing the intuitive essential characteristics of functions-contact and change; But at the same time, the new standard also highlights the view that function is the main line of algebra content in junior high school. Therefore, function learning is not a "brand-new" content in junior high school, so we need to pay attention to its continuity with primary school; At the same time, learning in junior high school is not theoretical, but mainly based on intuitive research; But it is necessary to introduce the relationship between function and equation, inequality and so on. Therefore, function is an important mathematical model to study the phenomenon of movement change, and it is the main line of junior high school mathematics and algebra.