Let D=(P,B) be a non-trivial block-transitive t-(k2,k,λ) design with G≤\Aut(D) and X⊴G≤\Aut(X), where X=PSL(n,q)(n≥3). We prove that t=2 and the parameters (n,q,v,k) is (3,3,144,12),(4,7,400,20) or (5,3,121,11). Moreover, D is a 2-(144,12,λ) design with λ∈{3,6,12} if λ∣k.