In this work, methacrylated castor oil (MCO) and methacrylated eugenol (ME) are prepared from bio-based castor oil and eugenol, respectively. The resulting MCO and ME are then mixed and cured to obtain an environment-friendly castor oil-based unsaturated polyester thermosets. The chemical structures and viscosities of MCO and ME are characterized by 1H NMR and Fourier transform infrared spectroscopy (FT-IR) . The curing degree, thermomechanical properties and thermal stability of the MCO-ME thermosets with different MCO loadings are systematically evaluated through DCS, gel content, DMA, TGA and so on. The results show that: when the mass ratio of MCO to ME is 40:60, the glass transition temperature of the MCO-ME thermoset is 19.7 ℃, the storage modulus at 25 ℃ is 288.8 MPa, the gel content is 91.4%, the residual carbon content at 800 ℃ is as high as 13.28%, confirming the MCO-ME thermosets have good thermal stability. Therefore, the prepared castor oil-based unsaturated polyester thermosets can be used as potential substitutes for petroleum-based unsaturated polyester thermosets.