With the increasing scale of modern power grid and the large-scale access of distributed generation， the problems of strong harmonic，high noise and dynamic signal change will reduce the accuracy of the synchronous phasor measurement algorithm. In order to accurately measure the synchronous phasor parameters of modern power grid，a algorithm based on the second-order Taylor dynamic phasor model and the improved matrix pencil is pro? posed，which can be used to accurately measure the amplitude and angle parameters of synchronous phasor in power system under dynamic conditions. Firstly，the algorithm is deduced mathematically，and then the measurement accu? racy is evaluated in detail according to the experimental cases specified in the test specification of synchronous pha? sor device in our country. The experimental results show that the algorithm has a high measurement accuracy under the conditions of frequency deviation and amplitude modulation，which meets the requirements of the detection specifications and has a certain engineering application value.