The invention provides a magnetic combined crosslinked enzyme aggregate biocatalyst. The biocatalyst can produce diffraction peaks at diffraction angles 2 theta of 30.5+ / -0.2 degrees, 35.4+ / -0.2 degrees, 44.7+ / -0.2 degrees, 57.3+ / -0.2 degrees and 63.4+ / -0.2 degrees. A preparation method of the biocatalyst is simple, does not need special equipment, needs mild process conditions, is easy to operate, realizes a low cost and is suitable for industrialization. The biocatalyst is used for asymmetric synthesis of (R)-3-quinuclidinol, realizes synchronous carbonyl reduction and coenzyme NADH / NAD<+> in-situ regeneration, prevents diffusional limitation to a substrate , a coenzyme and a product, has good catalytic activity and high catalytic efficiency, greatly shortens reaction time and has obvious economic values.