The invention discloses a subtend compression chirped pulse amplification laser system, comprising a seed source, a stretcher, a subtend compressor and a focusing mirror; the subtend compressor consists of a raster compressor, two polarizing beam-splitter plates, two polarization converters, one delayer and five reflectors. The subtend compression chirped pulse amplification laser system realizes the two-way time-sharing secondary utilization of the raster compressor, breaks through the limitation of the bearing capacity of the taster compressor, avoids the non-linear effect, has the identical dispersion compression amount and realizes multiplication of the output capability of the chirped pulse amplification laser system.