The invention relates to a method for preparing a combretastatin derivative (I) or (II), said method including the following steps: triaryl(3,4,5-trimethoxybenzyl)phosphonium halide P
3
(III), wherein Ar denotes an aryl group selected from among phenyl or thienyl, is reacted with P
2
having formula (IV) or P′
2
having formula (V) so as to respectively obtain the compound P
4
or P′
4
, which have formulas (VI) and (VII), respectively; then, during a step for deprotection in the presence of an acid and/or a base, the compound having P
4
or P′
4
leads, after an optional purification step, to the compound having formula (I) or (II).