The Fock-Bargmann-Hartogs domain Dn,m(µ) (µ > 0) in C n+m is defined by the inequality w 2 < e −µ z 2 , where (z, w) ∈ C n × C m , which is an unbounded non-hyperbolic domain in C n+m . Recently, Tu-Wang obtained the rigidity result that proper holomorphic self-mappings of Dn,m(µ) are automorphisms for m ≥ 2, and found a counter-example to show that the rigidity result isn't true for Dn,1(µ). In this article, we obtain a classification of proper holomorphic mappings between Dn,1(µ) and DN,1(µ) with N < 2n.. Alexander [1, 2] further studied proper holomorphic mappings between bounded domains with the same dimension. Alexander's theorem has been generalized to many classes of domains (e.g., see Bedford-Bell [3], Diederich-Fornaess [5], Huang [9], Su-Tu-Wang [17], Tu [19], Tu-Wang [20, 21], and Webster [22]). Inspired by these theorems, there are many results on classifying proper holomorphic mappings up to holomorphic automorphisms (e.g., see Dini-Primicerio [6], Ebenfelt-Son [7], Faran [8], Landucci-Pinchuk [11], Spiro [16], and Zapalowski [23]).The Fock-Bargmann-Hartogs domains D n,m (µ) are defined by D n,m (µ) := {(z, w) ∈ C n × C m : w 2 < e −µ z 2 }, µ > 0.