The molecular formula of Norsesquilerpenoid Lactone is C14H20O3. The crystal belongs to the orthogonal system, with space group D24-P21 21 21. The cell dimensions are α=7.526(3)?, b=24.642(10)?, c=6.887(2)?. Four molecules are contained in a cell (z = 4). Intensity data were collected on a RASA-IIS four circle diffractometer.The original MULTAN-80 was proved to be not successful in solving the structure. The correct structure solution was obtained by improving distribution of reflexion indexes.Finally, we analyse the cause of failure that original start set created and give reason for selecting new one.