A fabrication process has been optimized to produce photocatalytic H2La2Ti3O10/CdS nanocomposites by a stepwise exchanging reaction of H2La2Ti3O10 with n-C3H7NH2 (or n-C8H17NH2), Cd(CH3COO)2 and H2S gas, which was obtained by H+-exchanging reaction of K2La2Ti3O10 with HCl other than the normally used HNO3. XRD, TEM, FT-IR, TG, ICP and BET methods were used to investigate the pillaring-process. Results showed that the particle size of pillared cadnium sulphide was less than 1nm and the amount of intercalated CdS increased from 12.2 wt% to 16.5 wt% when n-C8H17NH2 took the place of n-C3H7NH2 to “pre-expand” the interlayer of H2La2Ti3O10. The possible reason of this success was mentioned. The photocatalytic properties of the resulting powders were evaluated by using photodecomposition of methyl orange as the model system. Compared with the unpillared K2La2Ti3O10, the pillaring of CdS gave rise to a remarkable enhancement of its photoactivity and the decomposition rate of methyl orange was improved from 50% to 95%.