Effect of α particles on the structural integrity of membranes and the morphology of rat erythrocytes is studied using the 120-cm cyclotron at the Skobel’tsyn Research Institute of Nuclear Physics of Moscow State University. Blood is irradiated in cells with walls made of thin mylar films; the gap between the walls does not exceed 1.0 mm. The energy of α particles entering the solution is 26.7 MeV. The linear energy transfer (LET) of α particles was approximately 24 keV μm−1. This value is close to the LET of relativistic nuclei of the neon-magnesium group in Galactic cosmic rays, allowing us to simulate their effect on biological objects. A number of stable changes that grew as the absorbed dose rate rose was detected in the irradiated samples.