Abstract
Cosmic no-hair conjecture states that all expanding universe models with positive cosmological constant asymptotically approach the homogenous and isotropic de Sitter solution. This conjecture has been proved under certain energy conditions and has also been supported by a number of expanding solutions realized for a few known models. We will study the evolution of a homogeneous Bianchi typeⅠmodel which provides a supporting evidence of the comic no-hair conjecture. This model modifies the Einstein’s equation by the inclusion of quadratic curvature terms. Anisotropic solutions will be solved along with another de Sitter solution. The anisotropic solution can be shown to be unstable by a perturbation method. The result provides a positive supporting evidence for the comic no-hair conjecture.