Abstract: In the present paper,deformation and fracture of specimen during the microshear test have been investigated by using a series of interrupted loading method.A concept on microshear toughness has been proposed and it represents the absorbed energy of sheared specimen,Moreover,it is indicated from the evaluation of an API X65 steel welds that the microshear test may be conveniently used to study the local mechanical properties and their distribution in practical welds with low expense,More informations given by the microshear test are available for the compilation of welding procedure and fracture analysis of welds.