In order to study rain island effect caused by urbanization development, the six-stage theory and the S-shaped curve method were used to analyze the level of urbanization development in Zhengzhou by means of the socio-economic data of Zhengzhou from 1978 to 2018 and daily rainfall data from 1960 to 2020, and evaluation method system of rain island effect was constructed by integrating multiple methods. Based on annual precipitation and annual flood season precipitation, the trend and periodic change analysis of rain island effect in Zhengzhou was carried out, and the normalized distance method was introduced to quantitatively evaluate the rain island effect. The results showed that the rain island effect in central urban area of Zhengzhou had an obvious trend of abrupt increase in 1997 and 2004; the increasing trend of rain island effect of annual precipitation and annual flood season precipitation lasted for 4 years and 10 years, respectively, with the first main period of 8 to 10 years and 15 to 20 years and the second main period of 17 to 20 years and 6 to 10 years, respectively; the explicit values of annual precipitation enhancement coefficient and annual flood season precipitation enhancement coefficient calculated by the standardized distance method were 0.261 and 0.643, respectively, indicating that the rain island effect in Zhengzhou was concentrated in flood season.