Abstract: It is of great significance to study the impact of offshore windfarms construction and operation on marine ecological space. Taking Tangshan laoting bodhi island offshore windfarms as an example, this paper identifies the affected factors in the marine ecological space such as birds, marine organisms and biodiversity, fishery resources and so on around the offshore windfarms. Based on the influencing factors of offshore windfarms and the affected factors in marine ecological space, on-site surveys and data collection of relevant data have been carried out. Combined with the measured data of electromagnetic environment and marine organisms, as well as the collected data of noise and birds, the impact of offshore windfarms on marine ecological space is evaluated. The research results show that the noise of the offshore windfarms in the case area during the construction period is much greater than that during the operation period, and the electromagnetic interference above the sea surface and underwater is very little; The impact on marine ecological space is mostly concentrated in the construction period, with relatively small impact in the operation period.