The invention discloses a photovoltaic inverter islanding detection method and device. The method comprises the steps that whether output power of a photovoltaic inverter under the normal grid-connected operation situation and power consumed by local load is balanced is judged; if the judgment result is no, islanding detection is performed by using a passive detection method; if the judgment result is yes, islanding detection is performed by using an active detection method; the active detection method comprises the steps that the initial phase of output current of the photovoltaic inverter is calculated according to a langevin function; and whether the phase of common point voltage is constantly ahead of or behind the phase of output current is judged according to the phase angle of the load and the initial phase, and common point frequency is determined to exceed the range of preset frequency if the judgment result is yes and islanding occurs. The active detection method and the passive detection method are combined so that islanding can be effectively detected and reliability is high; meanwhile, the initial phase is calculated by applying the langevin function so that the positive feedback process can be accelerated, the islanding state can be detected as fast as possible and influence on the quality of electric energy is low.