Tilt growth is usually observed for the thin film growth on a substrate. Such tilt growth is considered as a consequence of the relaxation of the misfit strain between the epilayer and the substrate. In this paper, we propose a theoretical method to obtain the tilt angle of the epilayer, especially suitable for the heterostructure with large misfit strain which can be more than 10%. As an application of our method, we focus on two growth cases. One case is the growth of MnAs epilayer on GaAs (113) substrate with the lattice mismatch between the MnAs epilayer and the GaAs (113) substrate as high as 80%. And the other case is the growth of GaN epilayers on GaAs $\{1 \overline 1 l\}$ substrates. Results calculated from our method for the two cases agree well with the experimental observations. This method is general, and can be applied to other material systems with large lattice mismatch.