The theoritical and experimental study on the strain of loose-tube stranding optical cable has been done.The experimental instruments and samples are introduced.The experimental results show that fibers are not in tension when the strain of the cable is smaller than the fiber extra length

and the strain curve of cable is approximately linear.The variation of optical power in fibers and the strain approach zero when the cable sample is in the long term tension. The biggest variation of optical power in fibers is 0.023dB and the biggest fiber strain is 0.012% during the short term tension.