The invention relates to a method for preparing a protein isolate of the biomass of microalgae of the genus Chlorella, characterised in that it comprises the following steps: supplying a microalgal biomass produced by fermentation； optionally washing the biomass so as to eliminate the soluble interstitial compounds, thermal permeabilisation of the biomass at a temperature of between 50 and 150°C, preferably between 100 and 150°C, for between 10 seconds and 5 minutes, preferably between 10 seconds and 1 minute； elimination of the biomass permeabilised in this way by means of a solid-liquid separation technique selected from the group consisting of frontal or tangential filtration, flocculation and centrifuging, more specifically multi-stage centrifuging, in order to obtain a soluble fraction； optionally recovering and clarifying the soluble fraction thus obtained by microfiltration in such a way as to remove the residual insoluble elements therefrom； ultrafiltration of the soluble fraction on a membrane with a cut-off threshold lower than 5 kDa, preferably between 1 and 5 kDa, in order to produce a soluble protein isolate； then evaporation, pasteurisation and atomisation of said protein isolate.La invención se refiere a un método para preparar un aislado de proteínas a partir de la biomasa de microalgas del género Chlorella, caracterizado por que comprende las siguientes etapas: suministro de una biomasa de microalgas producida por fermentación； opcionalmente, lavado de la biomasa de manera que se eliminen los compuestos solubles intersticiales, permeabilización térmica de la biomasa a una temperatura de entre 50 y 150 °C, preferentemente de entre 100 y 150 °C, durante entre 10 segundos y 5 minutos, preferentemente entre 10 segundos y 1 minuto； eliminación de la biomasa permeabilizada de esta manera mediante una técnica de separación sólido-líquido seleccionada a partir del grupo constituido por filtración frontal o tangencial, floculación y centrifugación, más espec
