Abstract: According to the comparative analysis of non-thermal electromagnetic instability in liquid crystals by using a crystalline liquid biomembrane model, this paper has proposed that the key mechanism of non-thermal electromagnetic biological effects are based on the electrohydrodynamic instability of crystalline liquid biomembranes. This hypothesis can be used to explain satisfactorily the important properties of non-thermal electromagnetic biological effects such as nonlinearity, concertedness coherence, and windows, and thresholds properties.