Chemical industry plays an important role in the development of national economy and society, and imposes direct impacts on all other social and economic sectors. Meanwhile, due to chemical industry characteristics of both severe environmental pollution and high accident frequency, it also threatens the regional ecological environment, human health and life safety. From the perspective of industrial park admission rate of chemical enterprises, and based on the chemical enterprises detailed data, we systematically analyzed and revealed the spatial-temporal patterns and its influencing factors of chemical industry in the Yangtze River Delta from 1998 to 2013 with the integration of mean center, standard deviation ellipse, kernel density and spatial autocorrelation. The results showed that chemical enterprises exhibited a generally growing trend in the study area from 1998 to 2013 with a continuing rising admission rate from 6.19% to 36.98%. Chemical enterprises distributed in the ‘northwest-southeast’ direction, and approximately showed the ‘first southeast, then northwest’ migration path. Compared to other chemical enterprises, chemical enterprises in industrial park had a higher dispersion trend and a larger migration range. And chemical enterprises in industrial park gradually evolved from spatial mismatch to spatial match with all chemical enterprises. Central agglomeration coexisted with the peripheral diffusion, and four major chemical agglomeration areas formed in the Yangtze River Delta, namely Taihu Lake agglomeration area, Hangzhou Bay agglomeration area, Yangtze River concentrated area, and coastal concentrated area. The regional spatial structure of chemical industry tended to be complicated, orderly and stable. Industrial park admission rate of chemical enterprises presented significantly positive spatial autocorrelation in 2003 and 2013, with a rising trend at municipal level. Hot spots gradually transferred from southeast Zhejiang to northwest Jiangsu, Anhui, while cold spots moved from north Anhui to southwest Zhejiang, which led to the symmetry reverse transformation of spatial patterns of chemical enterprises. But industrial park admission rate and spatial density distribution of chemical enterprises had always been in the imbalance and mismatch state. Combined with chemical industry characteristics and the Yangtze River Delta regional features, we qualitatively discussed the influencing factors of the spatial-temporal patterns of chemical industry in the Yangtze River Delta, especially to elucidate the mechanism of park industrializa-tion process of chemical industry.