The present invention relates to a pharmaceutical composition with enhanced stability, containing pemetrexed or a salt thereof, and a preparation method therefor. The present invention provides an injection preparation in liquid form containing pemetrexed, capable of ensuring sufficient stability during circulation and storage by selection of an optimum material and setting of an optimum concentration range in order to secure the stability of pemetrexed. The present invention can provide a pemetrexed preparation which is readily commercially prepared, can prevent microbial contamination occurring during lyophilization or reconstitution, and has enhanced convenience of administration and stability.
