In Horava-Lifshitz gravity, the extra dynamical scalar mode could play significant role in cosmology. However it has been pointed out that such a scalar may suffer from the strong coupling problem in IR. We address this issue in this paper. Our analysis shows that the scalar mode could decouple naturally at \lambda=1 due to the extra gauge symmetry. On the other hand, the fact that the scalar mode becomes ghost when 1/3<\lambda<1 is a real challenge to the theory. We try to overcome this problem by modifying the action such that the RG flow lies outside the problematic region. We discuss the cosmological implications of the action and calculate the power spectra of scalar and tensor modes.