The　two-layer　computer　simulators　are　commonly　used　to　mimic　multi-physics　phenomena　or　systems.　Usually,　the　outputs　of　the　first-layer　simulator　(also　called　the　inner　simulator)　are　partial　inputs　of　the　second-layer　simulator　(also　called　the　outer　simulator).　How　to　design　experiments　by　considering　the　space-filling　properties　of　inner　and　outer　simulators　simultaneously　is　a　significant　challenge　that　has　received　scant　attention　in　the　literature.　To　address　this　problem,　we　propose　a　new　sequential　optimal　Latin　hypercube　design　(LHD)　by　using　the　maximin　integrating　mixed　distance　criterion.　A　corresponding　sequential　algorithm　for　efficiently　generating　such　designs　is　also　developed.　Numerical　simulation　results　show　that　the　new　method　can　effectively　improve　the　space-filling　property　of　the　outer　computer　inputs.　The　case　study　about　composite　structures　assembly　simulation　demonstrates　that　the　proposed　method　can　outperform　the　benchmark　methods.