The invention provides a forming method of a semiconductor structure, which comprises the following steps of: providing a substrate; forming a pseudo gate stacking on the substrate and forming a layer or multiple layer of side walls on the two sides of the pseudo gate stacking; injecting to form a source electrode and a drain electrode, and carrying out high-temperature annealing activation on the source electrode and the drain electrode; removing the pseudo gate stacking; etching the substrate below the pseudo gate stacking to form a groove; forming a channel strained layer in the groove; and forming a gate stacking on the channel strained layer. Through forming the channel strained layer with a gate last technology after carrying out the high-temperature annealing activation on the source electrode and the drain electrode, the invention can ensure that a high temperature step and a low temperature step have no mutual influence, therefore, the invention can not only guarantee the property of the channel strained layer, but also can ensure the activation rate of the source electrode and the drain electrode.