Increasing the transmited pulse width of optical time domain reflectometer(OTDR) may lead to saturation effect of ava-lanche photodiode(APD) in the detection circuit of OTDR, and makes the measured curve flat roof effect, which will submerge the short-range event results. To solve this problem, this paper proposes a multi-pulse width combined measurement method, the measurement results are software spliced to achieve a longer measurement distance under the condition of the hardware configuration unchanged, and the near-end events will not be submerged by the flat roof due to the saturated flat roof effect, the dynamic range of OTDR measurement is improved.