The main problems with the determination of mercury in foodstuffs by stripping voltammetry were analyzed. The conditions for obtaining the analytical signal from mercury(II) at a gold–graphite electrode and for reducing the effect of interfering substances were refined. A simplified procedure for the preparation of foodstuff samples by the chemical (HNO3 + H2O2) and photochemical oxidation of samples was proposed. The determination conditions were optimized by the fractional factorial design of the experiments. It was shown that a gas-discharge XeBr excilamp can be used as an alternative to a mercury quartz lamp in the sample preparation of foodstuffs. The conditions for reducing the blank experiment and its contribution to the results of determination were considered.