In order to realize high-precision mass production of small diameter dual aspherical chalcogenide glass lenses, cooling gap in cooling stage was studied to reveal its influence on lens molding quality through simulation and experiments. Firstly, high temperature viscoelastic mechanical, structural relaxation and interface heat transfer model of the chalcogenide glass molding was analyzed and applied to simulation study. Secondly, molding simulation of target lens was carried out, and influence of cooling gap conditions on internal temperature, stress distribution, and profile deviation of the lenses were discussed. Finally, the molding experiments corresponding to simulation were conducted. The influence of cooling gap conditions on the surface form accuracy PV, surface roughness Ra and profile deviation of the molded lenses were analyzed, and simulation and experimental results were also compared to verify the validity of simulation model and its results. Simulation results show that the stress was the smallest when cooling gap is 0.1 mm, which is 3.897 MPa. The profile deviations of molded lens ASP1 and ASP2 were 1.054 μm and 0.858 μm, respectively. The experimental results show that surface quality of molded lens with cooling gap of 0.1 mm was the best. The PV values of ASP1 and ASP2 are 170.8 nm and 223.6 nm respectively, Ra values are 22.7 nm and 24.9 nm respectively, and maximum profile deviations are 0.896 μm and 0.738 μm respectively. Therefore, minimum cooling gap is 0.1 mm. The simulation results showed good agreement with experimental results. The cooling gap has some influence on molding quality of small diameter dual aspherical chalcogenide glass lenses. The determination of minimum cooling gap can effectively improve surface quality of molded lenses.