The invention discloses a cyclo-octadiene complex containing a dinitrogen ligand low-valent metal rhodium (I) and a preparation method thereof. The method comprise the following steps: 1) anhydrous alcohol is taken as a solvent and acetic acid is taken as a catalyst, o-anisidine and pyrrole-2-formaldehyde are reacted to prepare a dinitrogen schiff base ligand 2-(pyrrole-2-methylene amino)anisole; and 2) under condition that inert gas protection and existence of dis(trimethylsilyl)amino strong base, the 2-(pyrrole-2-methylene amino)anisole ligand and a (1,5-cyclo-octadiene) rhodium chloride (I) dimer are subjected to a reaction in an organic solvent to prepare the cyclo-octadiene complex containing the dinitrogen ligand low-valent metal rhodium (I). The method has the advantages that the reaction yield is high, reaction steps and post treatment are simple, a structure of the obtained compound is unique, the complex contains low-valent rhodium metal ions and easily left cyclo-octadiene organic ligand, and is a latent catalyst for coupling and hydrogenation reactions.