IIn order to reveal the problems in welded joint of heat resistant steel, cold cracks and reheat cracks in 2.25Cr-1.6W steel are selected as the objects. Scanning electron microscopy（SEM） and electronic backscattered diffraction（EBSD） are used to study the effect of texture on the cold cracks and the effect of crystal boundary misorentation on the reheat cracks. The results show that the columnar crystals with different crystal orientation generate larger strain concentration,which led to the big angle shift of the main crack extension. In addition,phase transformation texture, namely microstructure,has a large effect on the concrete extension paths of the cold cracks. For reheat cracks,cavities and microcracks preferentially form at high-angle crystal boundaries. The proportion of high-angle crystal boundary rises with the increase of the plastic deformation caused by both temperature gradient and stress in the coarse grain heat affected zone,which are good for the nucleation and extension of reheat cracks.