Hydrothermal reaction of benzene-1,2,4,5-tetracarboxylic （Btec） dianhydride with La203 lead to a new organometallic compound, [La2（betc）（Hbtec）（H20）3][HCONH（CH3）2] （1）. Single-crystal X-ray diffraction analysis reveals that it crystallizes in monoclinic space group P21/n that mimics orthorhombic space group Pnma （viz. pseudo-merohedral twinning structure） with a = 7.6002（16）, b = 18.954（4）, c = 18.213（4） A., β = 90.121（3）°, V= 2623.5（9） A3, Z = 4, Mr= 907.21, Dc = 2.297 g/cm3, F（000） = 1752, μ（MoKa） = 3.32 mm^-1, R = 0.0575 and wR = 0.0956. The structure of I featres a 3-D framework constructed by La（III） cations, btec^4- ligands, Hbtec^3- ligands and coordinated water molecule. All of the La（III） cations are 10-coordinated by O atoms into 1-D infinite chains, which are further interconnected by C atoms of btec ligands to form a 3-D framework.
