The multifunctional nutrition analyzer, which integrates four detection functions, can make fast, accurate, quantitative analysis for a variety of nutrients. In this article we focus on researching the luminescence detection system. Compared with other means, luminescence detection needs no excitation light, and the detection sensitivity is improved due to the reduction of the background light. The apparatus consists of an displacement platform, a microporous plate, a combination of an aspheric lens and a plano-convex lens, an optical fiber and a photon counter connected with a computer. A theoretical light intensity formula is established as a reference and a comparison of the experimental data. In the experiment we applies ATP detection reagent as the experimental reagent, whose magnitudes of concentration are from 10-6 mol/L to 10-12 mol/L. The sensitivity of the apparatus could reach a magnitude of concentration of 0.1nmol/L, and it is estimated to be further improved by at least two magnitudes in theory with the system and the reagent optimized.