With the introduction of phasor measurement unit (PMU), measurable, observable and controllable level of distribution network can be greatly improved. Enormous challenges caused by the penetration of large-scale distributed generation and flexible load in post-modern distribution network can be solved. Distribution network can be promoted. In this paper, an adaptive phasor algorithm based on multi-self-calibration and multi-switching is proposed. Three modes of steady state, dynamic state and transient state are identified using multi-self-calibration, and algorithms adapting to three states are designed. In order to satisfy the requirements brought by the characteristics of PMU, this paper proposes a multi-self-switching method, which includes calibration algorithm, sensor type, sampling rate, window function type, data window length and synchrophasor algorithm. In order to further verify the superiority of the proposed algorithm, simulation analysis is carried out on simulation software. The results show that the proposed algorithm can meet the practical application requirements.