Abstract: A new three dimensional open-framework vanadium phosphate,[H3N(CH2)3NH3]2[H3N(CH2)3NH2][H2N(CH2)3NH2] [V(H2O)2(VO)8 ( OH)4 (PO4)4(HPO4)4]·4H2O(DAP-V9P8),has been hydrothermaly synthesized using 1, 3-diaminopropane(1, 3-DAP ) as structure-directing molecule and characterized by single crystal X-ray diffraction, infrared spectrum and thermogravimetric analysis. The compound exhibits a complicated framework structure consisted of corner-linked [VO5],[VO6], [PO4] and [HPO4] polyhedrons. There are interconnected channel system including a very large channel of 1.82nm of diameter in the structure. The 1,3-DAP molecules located inside the channels have three different conformations based on their crystallographic positions. It is noteworthy that the carbon chain of 1,3-DAP molecules in the center of the elliptical cavity is a linear type. Crystal data:a =1.4820(9) nm,b=1. 0255 (4)nm,c=1. 8181 (9)nm,β =90. 391(8)° ,P21/n (No.14) ,R1 =0.0772,wR2 = 0. 2004 (I＞(2σI)). Systematic structural comparison of DAP-V9P8 with isoframework compounds also been made.