Preformed particle gel (PPG) is a common lost circulation material to solve drilling fluid loss, but its swelling speed is too fast to cope with deep formation drilling fluid loss. This study aimed to design a high-strength preformed delayed expansion particulate gel (PDEPG) designed to address the disadvantage of conventional PPG's short equilibrium swelling time. The researchers created a comprehensive series of laboratory experiments to evaluate the delayed expansion and rheological properties of PDEPG under various conditions. To solve the problems of poor temperature resistance and low cross-linking density of traditional cross-linking agents, in this study, highly active microgels with surfaces covered with hydroxymethyl groups were prepared using acrylamide (AM) and N-hydroxymethylacrylamide (NAM), etc., which were co-polymerized with AM to form a first-order network in the presence of organic peroxides. Urea–formaldehyde (UF) resin was introduced as a second-order network to improve its temperature resistance further. This unique combination of first-order and second-order networks brings excellent heat resistance and delayed expansion to PDEPG. Swelling and rheological experiments show that PDEPG with a particle size of 1000 μm reaches equilibrium after expanding at 140 ℃ for 9 h with a swelling rate of 29.45 and storage modulus (G′) of 1450 Pa. In addition, it reached equilibrium after 7 h of expansion in a NaCl solution with a temperature of 140 ℃ and a concentration of 25.0%, with a swelling rate of 23.65 and G′ of about 6000 Pa. In the plugging experiment, PDEPG with a concentration of 4% and a particle size of 1000 μm was used to successfully plug the wedge-shaped fracture with an inlet of 3 mm and an outlet of 1 mm, and its pressure bearing capacity was 8.0 MPa. The experimental results show that PDEPG has excellent delayed swelling and pressure-bearing capacity, providing an alternative solution to address drilling fluid loss in high-temperature, high-salinity fractured formations.