The invention provides a steel strand prestress tensioning method, and belongs to the technical field of prestress tensioning. The method comprises the following steps that firstly, a tool clamping piece is arranged in an anchor band hole of a tool anchor band, a steel strand penetrates through a jack and the tool clamping piece in the anchor band hole, the steel strand penetrates through throughholes in a pushing plate, and an auxiliary clamp is fixed to the jack; secondly, the jack tensions the steel strand; thirdly, after tensioning is finished, reverse jacking is carried out; and fourthly, if the steel strand needs to be continuously tensioned, the first step is repeatedly executed, if the steel strand does not need to be tensioned, a connecting plate is reversely rotated, and a clamping part is separated from the edge of a piston. According to the tensioning method, a connecting plate of an auxiliary clamp is rotated, the clamping part is fixed to the piston on the jack, the auxiliary clamp can be well fixed, mounting is stable, the auxiliary clamp can be well prevented from falling, and safety of constructors can be ensured.