The test is based on a block with a strength of MU10.0, and after reviewing the literature, fly ash with a mass fraction of 20%, recycled aggregate with a replacement rate of 70%, and flax fibre with a volume fraction of 0.3% are added. The empirical formula is used to calculate and propose the ratio of recycled concrete with flax fibre, and a novel structural design for a self-insulated block is also proposed. The compressive and thermal properties of the self-insulated blocks were finally simulated using ANSYS finite element software, and it was discovered that the blocks’ stress distribution was uniform and stable, with a maximum stress value of 13.19 Mpa and a minimum stress value of 8.79 Mpa. Additionally, the distribution of the heat flow density is more even and stable, and the heat flow transfer is concentrated more in the left portion of the block. According to the energy conservation equation of heat flow steady state, the block’s simulated heat transfer coefficient is 0.416 W/(m2·K), which satisfies the numerical requirements of the current energy conservation design standards for homes in cold and cold regions.