Distribution network is seriously affected by harmonics and noise, the calculation of voltage phasor is more difficult, and the traditional phasor measurement accuracy of power transmission network can not satisfy the demand of distribution network. In order to improve the measurement accuracy of voltage amplitude and phase angle of distribution network, a method based on conditional maximum likelihood estimation (CML) is proposed for measuring the phasor of micro-synchronous phasor measurement unit (μPMU) in distribution network. The algorithm establishes the signal model of three-phase unbalanced system. When the measurement is up to two unknowns and the orthogonal value of the measured matrix and the unit matrix is not equal to zero, the feature which the three-phase matrix is orthogonal to the eigenvector of the sample covariance matrix is used to obtain the measurement. Furthermore, the amplitude and phase expression of the voltage phasor are deduced by the geometric characteristic, which reduces the computational complexity. Simulation test is carried out by Matlab, and the simulation results show that the proposed method can improve the measurement accuracy of the voltage amplitude and phase angle of distribution network to a certain extent.