In this work, we prepared the interpenetrating polymer networks of bismaleimide and polyether-type polyurethane(polyoxypropylene)-crosslinked epoxy (BMI/PU(PPG)-EP IPNs) by employing the simultaneous bulk polymerization technique. The polyurethane (PU)-crosslinked epoxy was identified via infrared (IR) spectra analysis. Also investigated herein were the mechanical properties, including tensile strength, Izod impact strength, and fracture energy (G(IC)) of the IPNs with various BMI contents in PU-crosslinked epoxy matrix. In addition, differential scanning calorimetry (DSC) analysis and the thermogravimetric analysis (TGA) were performed to examine the thermal properties of the BMI/PU(PPG)-EP IPNs. In addition, morphology and dynamic mechanical analysis (DMA) of the BMI/PU(PPG)-EP IPNs were also studied.