We study an elliptic system coupled by Monge--Amp\`{e}re equations:⎩⎨⎧detD2u1=(−u2)αdetD2u2=(−u1)βu1u1=u2=0amp;in Ω,amp;in Ω,lt;0,u2amp;on ∂Ω,lt;0amp;in Ω,%here Ω~is a smooth, bounded and strictly convex domainin~RN, N≥2, \alpha >0, \beta >0. When Ω isthe unit ball in RN, we use index theory of fixedpoints for completely continuous operators to get existence, uniqueness results and nonexistence of radial convex solutions undersome corresponding assumptions on α, β. When \alpha>0,\beta>0 and αβ=N2 we also study a~corresponding eigenvalue problem in more general domains