In order to solve the problems of food production and processing sites, such as the unfixed location of health inspection and the great influence of environmental factors on the inspection effect, according to the characteristics of different kinds of food residues under ultraviolet irradiation, a handheld fluorescence imaging device was developed by using fluorescence imaging technology and block Otsu algorithm, which can assist field inspectors in carrying out visual health inspection. The equipment detected milk powder (the volume fractions are 50%, 33%, 20%, 10%, and 2%) and spinach residue (the volume fractions are 50%, 33%, 25%, 20%, and 10%) on the surface of three common materials (wooden board, stainless steel board, polyethylene board). The results show that the system can assist inspectors in carrying out health and safety inspections. The detection rate of spinach residue with different volume fractions on the surface of the three materials is 100%, the detection rate of milk powder residue with different volume fractions on the surface of the wooden board and the stainless steel board is 100%, and on the surface of polyethylene plastic plate, except for the residual part of milk powder with the volume fractions of 2%, the remaining volume fraction of milk powder residue can be effectively detected. This study provides a reference for the development of handheld sanitary inspection equipment in food processing places.