The invention relates to a dynamic synchronous signal orientation based grid-connection converter transient state control method. The method comprises the steps of (1) collecting three-phase power grid voltage and current signals; (2) obtaining a positive sequence voltage and a negative sequence voltage; (3) obtaining a positive sequence voltage phase signal and a negative sequence voltage phase signal; (4) obtaining errors of positive sequence and negative sequence phase-locking ring output synchronous signals; (5) obtaining dynamic positive sequence and negative sequence synchronous signals of accurate and synchronous power grid voltage positive sequence and negative sequence component phase signals; (6) obtaining current including direct current amount and double power grid frequencies in a positive and negative coordinate system; (7) obtaining feedback signals of positive sequence and negative sequence active power/reactive power currents; (8) obtaining an error signal; (9) obtaining positive sequence and negative sequence components; and (10) obtaining a voltage reference signal, wherein the voltage reference signal is modulated by an SVPWM module to obtain a switching signal for controlling a converter power device; and the switching signal is input to a grid-connection converter II and a grid-connection converter I. According to the transient state control method, effective control for the positive sequence and negative sequence components of the converter output currents is realized.