Utilizing the ERA5 daily reanalysis dataset provided by the European Centre for Medium-Range Weather Forecasts (ECMWF), an objective identification is carried out to obtain the Northeast Cold Vortex (NECV) during the winter season from 1979 to 2020 and the life cycle, intensity, spatial distribution, and number of active days of NECV are explored. Furthermore, an Index of Northeast Cold Vortex (NECVI) is defined to analyze the multiscale features of NECV activity. Based on NECVI, Singular Value Decomposition (SVD) and regression analyses were performed to examine the influence of NECV on winter temperatures in Northeast and North China (NE-N) on intraseasonal scale. Results showed that over the 42 years, there were a total of 266 occurrences of NECV activity during the winter season within the identification area (35°N -60°N, 115°E -145°E), mainly located in the northern part of the identification area (45°N-60°N, 115°E-145°E), with an average life cycle of 4.3 days. The NECV activity does not show a significant linear trend or interdecadal variability, but there is a robust interannual variability with the main period of 2.2-2.5 years, while the intraseasonal oscillation period of the winter NECV is primarily 10-40 days. The SVD and regression analysis indicate that when there is a large-scale low-frequency cold temperature event occurs in the NE-N region, there lies a zonally low-frequency wave train with alternating positive and negative centers from the high-latitude areas of Western Europe to Northeast Asia, meanwhile, the Northeast region is often accompanied by strong cold vortex activity, and the occurrence of low-frequency cold temperatures in the NE-N region lags the low-frequency NECV by about 3-5 days.