To reduce the requirement for synchronization and improve the efficiency, safety and reliability of phase detection, an algorithm suitable for different voltage levels is proposed. A high voltage wireless phase detector is developed based on the charge-sensing principle of the flat capacitive electric field sensor and the method of zero crossing detection and waveform transformation. The principle of single-rod asynchronous phase detection is analyzed and the error is corrected. Transmission lines with different voltage levels and flat capacitive electric field sensors are modeled and simulated. The method is designed and debugged successfully for the hardware and software functions of the phase detector and the intelligent phase detection management platform of a mobile APP. In addition, the phase detection test is carried out under high voltage conditions. The results show that the non-contact high voltage phase detector can realize the single-rod and multi-point asynchronous phase detection in an environment of a high voltage electric field, and the phase detection results are stable and reliable. This work is supported by the National Natural Science Foundation of China (No. 51577022).