Abstract: Fast and accurate synchronous measurement data is the foundation for achieving closed-loop control of power systems, and short time window frequency measurement is the key to shortening the reporting latency of phasor measurement units (PMUs). However, existing short time window frequency measurement methods may result in significant measurement errors due to their inability to effectively filter out the fundamental negative frequency and harmonic components. To address the contradiction between measurement accuracy and reporting latency, this paper proposes an enhanced three complex bandpass filter for short time latency frequency measurement. This method combines the complex bandpass filter filtering with the reconstruction and elimination of the negative frequency components, and proposes a short time window negative frequency components suppression method; Furthermore, a harmonic suppression method based on adjusting the weights of three complex bandpass filters is proposed, and a frequency calculation error model containing harmonic components is established. The mechanism of the influence of harmonic components on the frequency measurement method of dual complex bandpass filters is revealed. By adjusting the weights of the three complex bandpass filters, the sensitivity of the algorithm to even harmonics is reduced, and accurate frequency measurement at single and 1.5 cycles was ultimately achieved. Simulation and experimental testing show that the proposed method is superior to existing frequency measurement methods and can provide short-term delayed frequency measurement data for applications such as closed-loop control in power systems.