A microstructure of filamentary Hg1223 superconductor by using CaHgO 2 for a vaporizing material was studied to improve the grain alignment and the transport J c . A. filamentary precursor Ba 2 Ca 2 Cu 3 Re 0.2 O x was fabricated using a solution spinning method and partially melted in an evacuated quartz tube with a pellet of (CaHgO 2 )Ba 2 CaCu 2.8 Re 0.2 (CuF 2 ) 0.2 O x . The reacted sample was a single phase of Hg1223 with T c value of 135 K. Platelike grains were partly aligned along the fiber length by controlling the heating condition. The J c value of the sample enhanced by using CaHgO 2 in stead of HgO for the vaporizing material. Although the J c value rapidly decreased by applying the field less than 0.1 T, the superconductivity at 77 K of the sample maintained in the field up to 8T.