NOVELTY - A crystal form of (-)-6-((4R,5S,6S)-2-mercapto-6-((R)-1-hydroxyethyl)-4-methyl-7-oxo-1-aza-bicyclo(3.2.0)hept-2-en-3-yl)-S-(6,7-dihydro-5H-pyrazol(1,2-a))(1,2,4)triazole onium salt has main peak at Bragg angle (2 theta ) of 16.228 plus minus 0.2 degrees , 15.602 plus minus 0.2 degrees , 18.017 plus minus 0.2 degrees , 20.178 plus minus 0.2 degrees , 20.669 plus minus 0.2 degrees , 22.108 plus minus 0.2 degrees , 24.354 plus minus 0.2 degrees , 27.155 plus minus 0.2 degrees , 28.320 plus minus 0.2 degrees and 29.766 plus minus 0.2 degrees , based on X-ray powder diffraction pattern.    USE - Crystal form of 6-(4R,5S,6S)-2-mercapto-6-(R)-1-hydroxyethyl-4-methyl-7-oxo-1-aza-bicyclo-hept-2-en-3-yl-S-(6,7-dihydro-5H-pyrazol)triazole onium salt (claimed).    ADVANTAGE - The high-purity crystal form of 6-((4R,5S,6S)-2-mercapto-6-((R)-1-hydroxyethyl)-4-methyl-7-oxo-1-aza-bicyclo-hept-2-en-3-yl)-S-(6,7-dihydro-5H-pyrazol)triazole onium salt having uniform crystalline particles and favorable stability in bright, hot and humid environments is economically prepared by simple method.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of crystal form of (-)-6-((4R,5S,6S)-2-mercapto-6-((R)-1-hydroxyethyl)-4-methyl-7-oxo-1-aza-bicyclo(3.2.0)hept-2-en-3-yl)-S-(6,7-dihydro-5H-pyrazol(1,2-a))(1,2,4)triazole onium salt, which involves adding crude (-)-6-((4R,5S,6S)-2-mercapto-6-((R)-1-hydroxyethyl)-4-methyl-7-oxo-1-aza-bicyclo(3.2.0)hept-2-en-3-yl)-S-(6,7-dihydro-5H-pyrazol(1,2-a))(1,2,4)triazole onium salt in primary solvent, then adding secondary solvent, controlling temperature at 5-25 degrees C for 2-4 hours to crystallize, and performing solid-liquid separation, to obtain crystal form of (-)-6-((4R,5S,6S)-2-mercapto-6-((R)-1-hydroxyethyl)-4-methyl-7-oxo-1-aza-bicyclo(3.2.0)hept-2-en-3-yl)-S-(6,7-dihydro-5H-pyrazol(1,2-a))(1,2,4)triazole onium salt. The primary solvent is water and/or ethanol. The secondary solvent is ethyl acetate, acetone, ethanol and/or ethyl formate.