Abstract: Microplastics (MPs) with a growing trend in the global ocean provide new habitat and dispersal vectors for microalgae, those microalgae attached to MPs are referred to as Epimicroplastic microalgae (EMP-MA). Research on EMP-MA can be traced back to 1971, but the concept of EMP-MA was not formally proposed until 2022 and is gradually gaining attention due to increasing pollution from MPs. Algae such as diatoms, dinoflagellates, cyanobacteria and green algae can attach to MPs, where diatoms are the most abundant and diverse taxa with common diatoms including Achnantes, Amphora, Cocconeis, Navicula, Nitzschia, etc. It is worth noting that in the EMP-MA community it presences some harmful algae such as Ostreopsis cf. ovata, Alexandrium pacificum, Gonyaulax spinifera, Prorocentrum donghaiense, Pseudo-nitzschia pungens, etc. They may be transferred to other regions with MPs driven by wind and currents, providing seeds and increasing the risk of outbreaks and spread of HABs. And this risk is likely to increase with growing pollution from MPs and changing global climate.However, no study reported that those harmful algae attached to MPs have caused harmful algal blooms (HABs) or dispersal of HABs. Therefore, we should continue to pay attention to the spatial and temporal dynamics of harmful algae attached to MPs, actively establish a risk assessment system and carry out in-depth research on the possibility of HABs or the key environmental factors causing HABs, so as to exploit the mechanism of HABs outbreaks and dispersal, and to provide a theoretical basis for the work of marine disaster prevention and mitigation.