A photoresist is composed of an alkali soluble resin, a photosensitive agent and a solvent. The alkali soluble resin includes a first type novolak resin synthesized from meta-cresol, and the first novolak resin has an average molecular weight of about 8000 to 25000 and a polydispersity index of four or less. The content of the first type novolak resin in the alkali soluble resin is about 5 to 30 wt. %. The photoresist can further include a second type novolak resin synthesized from a mixture of meta-cresol and para-cresol. The second novolak resin has an average molecular weight of about 2000 to 6000, and the weight ratio of meta-cresol to para-cresol is 4:6. The content of the second type novolak resin in the alkali soluble resin is about 70 to 95 wt. %.