The measurements of low angle X-ray diffraction showed that the degression of d(0) of lamellar liquid crystal with increase of weight ratio of CnOH/SDS decreased with increase of the carbon chain length of alcohol used aseosurfactant. The values of d(0) increased with carbon number of alcohol n at certain weight ratio of CnOH/SDS. The increase of interlayer spacing d with n was related with the increase of d(0) and the decrease of solvent penetration in lamellar liquid crystal under the conditione of weight ratio of CnOH/SDS and water content. Both the measurements of low angle X-ray diffraction and the phase diagram behavior showed that the stability of lamellar liquid crystal increased with the chain length of alcohol.