AlCrCuFeNb_xNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys were prepared by arc melting, and the effect of different Nb content on the microstructures and mechanical properties of AlCrCuFeNb_xNiTi high-entropy alloys was studied. The results show that the phase of AlCrCuFeNb_xNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys consists of ordered FCC L2₁ phase and Laves phase, together with minor BCC(A2) and FCC phases. The addition of Nb element can promote the formation of Laves phase and has a certain inhibitory effect on the segregation of Cu elements; The phase formation criterion suitable for AlCrCuFeNb_xNiTi high-entropy alloys is found through the calculation of phase criterion parameters; the addition of an appropriate amount of Nb can improve the mechanical properties of AlCrCuFeNiTi six-element high-entropy alloy; AlCrCuFeNb_0.5NiTi high-entropy alloy has better comprehensive mechanical properties. The compressive strength reaches 1587.4 MPa, and the hardness reaches 568.8 HV. When the Nb element content is too high, too much Laves phase will be formed and the alloy will exhibit premature embrittlement.