A series of vinyl pyrrolidone and vinyl acetate copolymers with different monomer ratios and homogeneity in backbone distribution were synthesized and their solution properties studied. In water, the phase diagram curve is concave, with the lower critical solution temperature, due to the cooperation of hydrophobic and hydrophilic hydration. In order to make a substantially homogeneous copolymer, a new method to determine the monomer mole fraction is suggested. When the vinyl pyrrolidone to vinyl acetate mole ratio in the copolymer is close to unity, sequence distribution plays an important part in solution behavior. The more homogeneous the structure, the better the solubility in water, and the higher the cloud point. This is attributed to the balance between hydrophobic and hydrophilic forces in solution. Copolymerization kinetic analysis on monomer conversions and turbidity measurement on poly(vinylpyrrolidone/vinyl acetate) solutions give consistent results to confirm this interpretation.