Metals are usually developed their performance in associated applications and their weldability has been on the second degree of importance. Therefore, a great number of studies have focused on the weldability problems of new materials. Solidification cracking is only one of these proplems that is common in the welding of stainless steels, aluminum alloys and high strength steels. Solidification cracking usually takes place in the weld centerline in the mushy zone. Low ductility of weld metal in solidification temperature range combined with tensile stress-strain in this region prone the material to hot cracks. Most of the studies about hot cracking have been from the mettalurgical aspects. Improving the chemical composition of electrode and imroving welding parametrs to prevent hot cracking has usually been the subject of these studies. Because a huge number of parametrs affect on hot cracking and because its very diffcult to develop mathematical models that describle them, mechanical aspects of hot cracking have less been studied. The few studies that exist in this aspect are about the prediction of hot crackign in casting and hot cracking in welding (both prediction and propagation) has less been studied. The subject of this study is to model both initiation and propagation of hot crack in autogenous welding of austenitic stainless steel 310s. The ABAQUS finite element program has been used. Analysis is accomplished in two decouple steps. In the first step, a thermal analysis is done in which the heat input is imposed to the plate by a suitable heat flux. The temperature history of nodes is used as the thermal load for the subsecuent mechanical analysis in which the stress-strain responce is developed. For mechanical analysis, a thermo-viscoplastic constitutive equaion with kinematic work hardening was used as the material constitutive behavior. Parametrs of this equation was extracted from some static and dynamic tension tests at high temperature. The effect of viscosity at high temperature, anealing and solidification shrinkage was implemented in the constitutive equation. For mushy zone and cracked elements an elastic perfectly plastic constitutive equation with 0.01 Mpa yield strength was used. Strain relaxation method was used to treat the fusion zone. To verify the developed model and method of study some experiments were also accomplished. Finally, the effect of the above-mentioned parameters and the effect of welding parametrs on hot cracking were studied. This study showed that maximum strain criterion could be used to predict hot cracking initiation and propagation. A thermo-viscoplastic constitutive equation with kinematic work hardening and an elastic-perfectly plastic constitutive equation were used to describe the behavior of base and weld metals respectively. Eliminations of viscosity leaded to a larger crack. An isotropic work hardening leads to a larger crack too. Parameters that affect on the weld pool shape had the most effect on the hot crack length. An increase in the heat input such as reducing the welding velocity leaded to a considerably larger crack. Stress-strain relaxation effect of the weld pool was one the most important parameters. This causes the weld metal to cool from zero stress-strain and causes the tensile stress-strain devolopes behind the weld pool. Annealling effect of the weld pool had significant effect on the results too. The results showed that annealing could be considered as a linear function of temperature that starts from half of the melting temperature (in kelvin) and completes at the melting temperature. Keywords : solidification cracking, weld, finite element, anneal, strain relaxation, thermo-viscoplastic, solidification shrinkage.