Optical frequency domain reflectometry (OFDR) is an optical detection technique based on frequency-domain analysis. It can achieve high-spatial-resolution distributed fiber temperature/strain sensing through a cross-correlation algorithm and has great application prospects in the structural health monitoring of spacecraft, flight vehicles, etc. Common cross-correlation algorithms have problems of small range and large amounts of computation in OFDR fiber temperature and strain sensing demodulation, which limits the large-range application of OFDR and the improvement of the demodulation rate. For this reason, a cross-correlation algorithm based on an adapted range was proposed. The algorithm not only improves the range of temperature and strain measurement but also enhances the demodulation efficiency of the system. Experimental results show the feasibility and efficiency of the proposed algorithm. The demodulation efficiency was increased by 2.25 times. The large-range temperature curve from 20 ℃ to 500 ℃ was measured, and the residual error of cubic curve fitting was less than 0.1 ℃. The test error was no greater than 5 με in the strain range of ±3000 με.