The invention discloses a method for preparing 
levodopa by virtue of an enzymic method. The method comprises the following steps: picking up an annular 
stenotrophomonas maltophilia strain slant for 
inoculation into a seed culture medium for culturing, thereby obtaining a primary seed liquid; inoculating a 
fermentation culture medium with the primary seed liquid at the inoculum size of 3-10% for 
fermentation culturing, centrifuging after the 
fermentation is ended and collecting bacterial cells; and adding 
tyrosine and the bacterial cells to a 
buffer solution to have an enzymatic reaction under the conditions of 18-30 DEG C and the pH of 5.0-6.0, thereby converting the 
tyrosine into the 
levodopa. According to the method, due to the 
resting cell transformation technology, and the preferred intermittent weak ventilation technology, adopted in the transformation process, the 
catalytic efficiency of the 
enzyme is improved; the concentration of the 
levodopa is 27g / L and the 
molar transformation rate of the 
tyrosine is above 99%; and besides, the method is mild in conditions, high in enantio-selectivity and free from 
racemization effect, is more suitable for industrial production, and has remarkable economic benefit and industrial application value.