Abstract: The four principal components, vitamin B₁, B₂, B₆ and nicotinamide in vitamin B compound tablet show certain instabilities individually and the amounts of these components differ considerably in the tablets, so their simultaneous determination without prior separation is usually difficult. This paper deals with the feasibility of using Kalman filtering spectrophotometry to do so, and makes some efforts concerning the deviation from the Beer-Lambert law due to mutual effects among the acting molecules. The results obtained were comparatively satisfactory both in precision and in accuracy. The average recovery of vitamin B₁, B₂, B₆, and nicotinamidewere 100.2+0.90% (CV), 100.3±1.7% (CV), 101.1+3.3% (CV), 99.90+0.65%(CV) respectively and were better than those in previous reports. All these show that the use of Kalman filtering spectrophotometry to the assay of vitamin B compound tablets is feasible.