In the present paper, the behavior of a single polymer chain under various solvent conditions was modeled by self-avoiding walks (SAW) with nearest neighbors attraction △ε on a simple cubic lattice. Determination of the θ-condition was based on the numerical results of the mean square radius of gyration and end-to-end distance. It was found that at the θtemperature △ε/kT equals -0.27. The exponents α in the Mark-Houwink equation with different interaction parameters are consistent with the results of experiments: under θ-condition, α= 0.5, and for a good solvent α = 0.74-0.84, respectively.