The reliability of Wide Area Measurement System (WAMS) advanced applications is highly dependent on the accuracy of PMU data. Presently, Total Vector Error (TVE) is usually adopted as an index for Phasor Measurement Unit (PMU) performance evaluation. However, TVE does not take frequency error into account, and is applicable only in laboratory, where the characteristics of test signal are given. With more and more PMUs put into field operation, it is a pressing task to develop a comprehensive index to evaluate PMU’s field performance. The objective of phasor measurement is to truly reflect the characteristics of sinusoidal signals in power system. Suppose that a sinusoidal signal is reconstructed from PMU measurements. In an ideal case, the difference between the reconstructed signal and original signal should not contain any components of fundamental frequency. Based on this idea, Total Phasor Error (TPE) is proposed to evaluate PMU’s field performance. Taking amplitude error, phase angle error, and frequency error into account, TPE is a comprehensive index hardly affected by harmonics and noise. It’s not necessary to know the characteristics of original signal to calculate TPE; hence, TPE is applicable not only in lab test, but also for field evaluation. Examples based on PMU data at North China Grid are given to demonstrate the reasonability and feasibility of TPE.