The effect of supply voltage and energy exposure on the photo signal value and signal-to-noise ratio is studied when the angle of incidence of optical radiation on the photosensitive surface of Ketek RM 3325, ON Semi FC 30035 and KOF5-1035 silicon matrix avalanche photodetectors are studied. A scheme of the installation and a research technique is given. The magnitude of the photo signal of the studied photodetectors were measured as a function of the magnitude of the overvoltage and the energy exposure of optical radiation, and the signal-to-noise ratios were determined. It has been established that the flat angle of view of silicon photomultipliers depends on the supply voltage of the photodetector and doesn’t depend on the energy exposure of optical radiation. Diagrams of the change in the magnitude of the photo signal from the angles of incidence of optical radiation on the photosensitive surface of photodetectors are presented as well. It has been found that at supply voltages exceeding the breakdown voltage by no more than 1 V, the maximum deviation of the angle of incidence of optical radiation on the photosensitive surface of silicon photomultipliers within the flat angle of view leads to a decrease in the signal-to-noise ratio to a component value of at least 60% of the maximum value for KOF5-1035 and at least 80% for Ketek RM 3325 and ON Semi FC 30035. The dependences of the signal-to-noise ratio on the angle of incidence of optical radiation on a photosensitive surface are given for various over voltages and energy exposures. The results of this article can be used in the development and design of instruments and devices for detecting optical radiation based on silicon photomultipliers.