The invention provides a Bayesian Decision Theory foreground extraction method combined with reflected illumination. The Bayesian Decision Theory foreground extraction method comprises the steps of appointing a 
point light source located on a foreground object by a user, carrying out 
gray level matching on an image, converting and imitating 
point light source illumination, strengthening 
image edge information, obtaining an illumination function according to before-after conversion comparison, filtering 
waves, reducing 
noise, dividing the image through a 
watershed algorithm, calculating a sectional drawing parameter through a Bayes formula, imitating an 
alpha value function curve through a multi-layer 
perception device, integrating the illumination function and a color 
distribution function, and completing extraction of the foreground object. The user is only required to appoint the position of the 
point light source and not required to preset edge information of a foreground and a background, the requirement for user interaction is reduced, meanwhile, 
time complexity of the used algorithms is series, and the defects that a common sectional drawing 
algorithm is large in calculated quantity and low in 
processing speed are avoided. Due to the facts that the illumination function is introduced and the 
alpha value is matched by the 
perception device, an accurate and complete extraction result can be obtained for the foreground object with complicated edges, and particularly for the foreground object similar colors of the edge and the ground.