Abstract: In this study, agar and maltodextrin were used as the main materials to prepare sustained-release capsules by the dipping method, and the influence of the ratio of agar/maltodextrin on the texture properties, rheology, and capsule performance and microstructure of the gel was investigated. The rheological test results showed that with the addition of maltodextrin, the viscosity coefficient K decreased, the flow index N increased, and the area of the thixotropic ring decreased. When the addition of maltodextrin exceeded 60%, it was impossible to prepare high-performance maltodextrin capsules. SEM results showed that agar and maltodextrin had good compatibility. The drying weight loss rate of the sustained-release capsule was less than 8.53%, the burning residue rate was lower than 1.15%, the crushing fragility was 0, the tightness was 0, and the encapsulation performance was good. In vitro release test results showed that the in vitro experiments capsule had good slow release effect, and the release of pure gelatin capsules would be 14 h, different proportion of agar/maltodextrin hard capsule had the different slow release time, with the increasing of content of maltodextrin, the sustained release time was shortened. Therefore, agar/maltodextrin was a material for preparing hard capsules with different sustained-release rates, which could meet the sustained-release requirements of a variety of nutrients and drugs by adjusting their ratio.