The invention discloses a capacitance regulating method of a 1/3 capacitance regulating transformer with a balance winding and a Dyn junction capacitance regulating transformer. The capacitance regulating method comprises the steps of establishing loss boundary equations for large and small capacity operation under the same load based on a transformer loss model under unbalanced conditions, establishing a ternary function F(x, y, z) about positive, negative and zero-sequence currents according to the boundary equations, judging a magnitude relationship between a value of the function and 1, and determining an operation mode of the capacitance regulating transformer. The capacitance regulating method is of important guiding significance to electric energy quality governance and power gridenergy conservation and consumption reduction.