NOVELTY - Preparation of montelukast intermediate compound involves adding chlorinated quinoline compound (I), toluene, water, carbonyl reductase and coenzyme into reactor, reacting, detecting reaction endpoint, heating, adding diatomite, stirring, filtering, taking out toluene layer, washing with clean water, dehydrating to obtain hydroxy-substituted chlorinated quinoline compound (II) in toluene solution, adding methyl magnesium chloride in tetrahydrofuran solution into reactor, adding anhydrous cerium chloride, reacting under reflux, cooling until crystallized, suction-filtering and drying.    USE - Method for preparing montelukast intermediate compound (claimed) used for pharmaceutical chemical and biological chemical fields.    ADVANTAGE - The environment-friendly method has high selectivity, mild reaction condition, increased output and reduced cost. It does not need separation of intermediate compounds.    DETAILED DESCRIPTION - Preparation of montelukast intermediate compound of formula (III) comprises:    (A) adding chlorinated quinoline compound of formula (I), toluene, water, carbonyl reductase and coenzyme into reactor, reacting at 25-45 degrees C and pH of 6.5-7.5 for 25-60 hours and detecting reaction endpoint by thin layer chromatography;    (B) heating to 75-80 degrees C, adding diatomite, stirring, filtering, taking out toluene layer, washing with clean water and dehydrating until water content is less than 0.1% to obtain hydroxy-substituted chlorinated quinoline compound of formula (II) in toluene solution;    (C) adding methyl magnesium chloride in tetrahydrofuran solution into reactor, adding anhydrous cerium chloride, reacting under reflux for 5-7 hours and cooling to - 10 degrees C; and    (D) adding dropwise compound (II) in toluene solution, reacting at - 15 to - 10 degrees C for 2-5 hours, detecting reaction endpoint by thin layer chromatography, adding quenching agent, quenching reacting, washing with water, concentrating solvent, cooling until crystallized, suction-filtering solvent and drying.