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Based on the lightning location detection data of Zhejiang Province from 2016 to 2020, the return-stroke characteristics of cloud-to-ground flashes in the land of Zhejiang Province and Zhoushan sea area are statistically analysed by using Access and MATLAB. The results are as follows: the annual average density of cloud-to-ground flash return strokes in Zhejiang Province is 1.97 fl·km^-2·a^-1; the density of positive cloud-to-ground flash return strokes is 0.10 fl·km^-2·a^-1; the positive cloud-to-ground flash return strokes accounted for 5.1% of the total cloud-to-ground flash return strokes; the average current intensity of positive cloud-to-ground flash return strokes is 42.49 kA; the average current intensity of negative cloud-to-ground flashes return strokes is 33.61 kA; the positive and negative current intensity ratio is 1.26; the annual average density of cloud-to-ground flash return strokes in the Zhoushan sea area is 0.54 fl·km^-2·a^-1; the density of positive cloud-to-ground flashes return strokes is 0.06 fl·km^-2·a^-1; the positive cloud-to-ground flash return strokes accounted for 11.1% of the total cloud-to-ground flash return strokes; the average current intensity of positive cloud-to-ground flash return strokes is 49.81 kA; the negative cloud-to-ground flash return strokes is 47.77 kA; and the positive and negative current intensity ratio is 1.04. The positive and negative return stroke currents in the northern region of Zhejiang Province and Zhoushan sea area are significantly stronger than those in the southern region. The average positive and negative return stroke current intensities in the Zhoushan sea area are stronger than those in the land of Zhejiang Province. The ratio of positive and negative return stroke current intensities in the Zhoushan sea area is significantly smaller than that in the land of Zhejiang Province. The ratio of average current intensities between positive and negative cloud-to-ground flash return strokes is quite different in different regions. The proportion of positive cloud-to-ground flash return strokes is particularly high in the Zhoushan sea area. The average current intensity of positive cloud-to-ground flash return strokes is slightly higher than negative, the causes of which are preliminarily explained by analysing atmospheric electricity and meteorology.