Two liquid crystalline (LC) epoxy resins consisting of LC diepoxide and LC hardner were synthesized, diglycidyloxyazoxybenzene (DGA), 4,4′-bis (ω-carboxy decanoxy) azoxybenzene (CAA10) and DGA with 4, 4′-bis (ω-hydroxy undecanoxy) azoxybenzene (HAA11), and their reaction mechanism, mesomorphic phase transition and thermal expansion were investigated by use of DSC, IR, polarized microscopy, X-ray diffractometry and capillary dilatometry. The fully gelated DGA-CAA10 formed a network structure in which one interchain crosslink was made per 5.6 repeating unit, and showed no mesophase. The DGA-HAA11 of linear typed polymer showed a smectic A phase when not fully cured, while a namatic phase when gelated. It was pointed out that the mesogenicity of epoxy resin is governed by the mesogenicity of monomers but is also correlated with the crosslinking density and degree of polymerization. In the fully gelated DGA-CAA10, thermal expansion coefficient (α) was about 2.2 × 10−4°C−1below Tg and 3.4 × 10−4°C−1above Tg, while about 2.3 × 10−4°C−1below Tg and above 6.5 × 10−4°C−1above Tg in the fully gelated DGA-HAA11. It is noted that the α value for DGA-CAA10 is low even above Tg.