Dislocations and stacking faults in silicon webs were observed and analysed by means of X-ray projection topographic method. Large area stacking faults parallel to the web surface have been found in as-grown specimens. In addition to the edge-, screw-, and 60°-type total dislocations with Burgers vector 1/2, and edge-type Shockley partial dislocations with Burgers vector 1/6, 30°- and 60°-type Shockley partial dislocations with Burgers vector 1/6 have also been discovered in the webs. These total dislocations move during heat treating at high temperatures and interact with other ones to form nearly hexagonal dislocation networks. Several dislocation reactions in a single slip plane have been found. The configuration and contrast of stacking faults in as-grown webs were changed by high temperature annealing. That can be explained by the moving of extended dislocation pairs, and the overlapping of stacking faults with each other in different layers. The extinction rule of image of Shockley partial dislocations was invalidated by the presence of impurity segregations. Dislocations within the stacking fault image were also observed. The experimentally observed results were analysed and discussed briefly.