To improve the physical properties of rice starch (RS) and expand its application fields, analytical techniques such as rheological analysis, scanning electron microscopy, low-field nuclear magnetic resonance, and X-ray diffraction were used to systematically examine the influence of curdlan (CL) addition on the structure and properties of the thermally irreversible gel of CL-RS blends. When the CL amount reached the threshold of 0.60%, compared with the control group, the gelatinization temperature decreased by 1.69 ℃, retrogradation viscosity increased by 25%, syneresis rate reduced by 47.73%, and transverse relaxation time T22 decreased by 58.01% to 6.45 ms. Compared with the group with 0.40% CL addition, the peak value of the storage modulus increased by 40.20%, the G′ value at the end of cooling increased by 21.46%, and chewiness improved by 24.76%. When the CL addition amount was 0.60% or less, retrogradation viscosity, viscoelastic modulus at each phase-change temperature node, chewiness, and the ratio of the bound-water peak area (A21) increased significantly with the increase in CL addition amount, whereas the transverse relaxation times T22 and T23 of water molecules and gel syneresis rate consistently decreased. The microstructure exhibited a decrease in porosity along with an improvement in the uniformity of its distribution. When CL addition exceeded the threshold (0.80%), a reduction of 11.37% in G′ at the end of cooling and a 42.89% decrease in chewiness were observed, accompanied by transformation of the microstructure from a porous network to a densely layered structure. The mechanism was attributed to CL-induced enhancement of hydrogen-bond crosslinking density, which facilitated the formation of stable threedimensional RS networks. In conclusion, properties of the RS-based blend gel were effectively regulated by the threshold effect of CL addition amount. These findings provide a theoretical reference for the development of new foods with RS-based heterogeneous polysaccharide blend systems.