Polyurethane (PU) prepolymer was first prepared via introducing double bonds on-to the PU chains, and then polyurethanepoly (butyl methacrylate) (PUPBMA) hybrid latex was prepared via miniemulsion polymerization. Transmission electron microscopy, Differential scanning calorimeter (DSC), Fourier transform infrared, and dynamic mechanical analysis were adopted to characterize the hybrid latex and its coating film. Both the coating property and the miscibility of PUPBMA emulsion have been greatly improved through introducing double bonds into PU prepolymer. With an increase in the molecule weight of PU (MPU), the increase in the particle size of PUPBMA emulsion was observed plus decreases in the stability of the hybrid latex and conversion of methacrylate. Besides, as MPU increased, the final dried coating film of the hybrid latex showed decreased water resistance, weakened miscibility, and improved mechanical properties. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011