1. A method for banknote identification based on thickness signal identification, comprising: acquiring a thickness signal of a banknote; preprocessing the thickness signal; identifying the thickness signal using an upward area identification method to acquire an upward processing identification result; identifying the thickness signal using a downward area identification method to acquire a downward processing identification result; merging the upward processing identification result and the downward processing identification result according to a preset rule to acquire a merging result; and identifying the merging result to acquire an identification result.