In this talk we summarize the results of measurements of the Tevatron LowBeta optics performed on May, 13. Based on the experimental data, we build the model of accelerator. The model takes account of gradient errors, including coupling, BPM gain errors, and BPM rolls. Strong sources of betatron coupling have been found at D16 and A38 locations, which is consistent with technical data. Having a reconstructed optics is essential for future improvements of the Tevatron performance.