The fine structure of the dislocation pits, which are formed by HCl-Fe+++ etching solution, is observed experimentally. The correlation between structure features of the dislocation pits and the directions as well as slip planes of the dislocations is investigated. We discussed the kinetic processes in which the etch pits are formed. The results indicated that different rate of nueleation and velocity of lateral motion on the dissolution steps of 〈112〉and〈112〉 crystal orientations is the main reason which makes the dislocation pits have two kinds of dissolute edges with different features.