The saturable absorption characteristics of Co ²⁺∶MgAl₂O₄ crystals in different cutting directions were experimentally studied. The anisotropic transmittance characteristics of [100] and [110]-cut Co ²⁺∶MgAl₂O₄ crystals were measured, and the measurement results showed that the crystal transmittance of [100] and [110] cutting directions changed periodically depend on the polarization direction of the incidence light. And, the output characteristics of two cutting directions of Co ²⁺∶MgAl₂O₄ passively Q-switched lasers in [100] and [110] are compared. Results show that the [110]-cut crystal has obvious advantages. The output energy is about 8% higher than that of the [100]-cut crystals, and the stability, beam quality, and extinction ratio are improved slightly.