Abstract: In order to obtain simplified calculation methods of ET0 in the conditions of lacking meteorological data in hilly area of central Sichuan Basin, the daily ET0 in Jianyang station from 1999 to 2005 was calculated by FAO-56 Penman-Monteith method, Hargreaves method, Hargreaves correction method, Priestley-Taylor method and Irmark-Alleen fitting method. ET0 calculated by PM method was used as the standard, Hargreaves correction method and Priestley-Taylor method had the minimum error, followed by Irmark-Alleen fitting method and Hargreaves method. Through the sensitivity analysis, the main meteorological factor affecting ET0 was relative humidity in hilly area of central Sichuan Basin. Therefore, the parameters of Irmark-Alleen fitting method used in humid climate were corrected month by month in the paper, and the calculation precision was improved obviously after correcting. Hargreaves correction method, Priestley-Taylor method and Irmark-Alleen fitting change method would be used for the calculation of ET0 in the conditions of lacking meteorological data in hilly area of central Sichuan Basin.