The invention discloses a deep-water solid-free water-based thermal insulation spacer fluid which is prepared from the components of superabsorbent resin, a tackifying agent, polyol, soluble salt, water, and an auxiliary agent. The solid-free water-based thermal insulation spacer fluid can be filled in oil and gas well downhole annulus and can perform a thermal insulation function. In deep-water oil and gas development, a seawater-section pipe column is in a low-temperature environment, such that the heat of passing formation fluid is dissipated fast. The temperature of the formation fluid drops sharply, and a hydrate risk is caused. With the spacer fluid, the risk can be solved. The thermal insulation spacer fluid system does not contain solid phase, such that solid phase deposition caused by polymer degradation is avoided. The spacer fluid also has the advantages of convenient pumping, low corrosion, good compatibility with downhole tools, no pollution to the marine environment, high thermal stability, and low thermal conductivity coefficient. Thermal insulation spacer fluids with different densities can be prepared with different types and different amounts of salt, such that the requirements by oil and gas reservoir with different pressure coefficients can be satisfied. The spacer fluid can be widely applied.