The green alga Chlamydomonas reinhardtii has been widely used to study many biological processes, including photosynthesis, flagellar motility, sexual reproduction, metabolism, and genetics. Here, we describe a step-by-step protocol of rapid and efficient transformation method for wild type cell-walled Chlamydomonas strains without cell-wall removal using a square electric pulses-generating electroporator. This method could be applied to the transformation of other industrially useful algae including diatom by optimizing the electric conditions.