Reference crop evapotranspiration (ET₀) is one of important climate factors, mainly affected by local climate. As related to water balance and energy balance, it decides the shaping and evolvement of geographical environment. With 34 meteorological stations'data including minimum and maximum air temperature, wind speed, air humidity and sunlight hours from 1951 to 2000, ET₀ was obtained by FAO Penman-Monteith equation (P-M) for growing season in western Songnen Plain of Northeast China. Then the authors analyzed the temporal- spatial characteristics of ET₀ series with climate diagnostic analysis, and the abrupt change points through point - area integrated analyses by J_y parameter and Mann- Kendall methods. The results show that: (i) the high value of ET₀ appears in southwest sandy land, and ET₀ gradually decreases northeastwards; (ii) ET₀ tends to increase in recent 50 years, and the north area contributes most; (iii) taking 1962 and 1982 as turning points, areal ET₀ series indicates evident phase changes during period of 1951~2000; and (iv) two upward and one downward abrupt changes are examined in areal ET₀ series, and the time of abrupt changes in typical stations is basically consistent with that in study area, but properties of abrupt changes show evident spatial diversity.