One of the main problems of lowland rice cultivation and production is the shortage of irrigation water, which effects the vegetative growth rate and the amount of yield and its component. In this study, afield experiment was conducted to find out the impact of some plant growth regulating substance on rice cultivars namely; Giza179 cultivar and Giza177 cultivar grown under different irrigation intervals in 2015 and 2016 growing season sat the farm of Agricultural Research Station, Sakha, Kafrelsheikh, Egypt. The Experiment was conducted using Randomized Complete Block Design with Strip-split plot arrangements. Main plots consisted of the three irrigation intervals namely; irrigation every 4 days (I1), irrigation every 8 days (I2) and irrigation every 12 days (I3), while sub plots devoted torice cultivars while the sub-sub plots contained the four levels of plant growth regulators: T1: spraying by cytokinein with concentration of 20 ppm, T2: spraying by abscisic acid with concentration of 15 ppm (ABA), T3: spraying by proline with concentration of 80ppm, T4: control (without any spray).The recorded data were chlorophyll content (SPAD), plant height (cm) at harvest, number of panicle (m-2), panicle weight (g), number of filled grains/panicle, number of unfilled grains/panicle, 1000- grain weight (g), grain yield (t/ha) and straw yield (t/ha). The main results indicated that irrigation every 4 and 8-days intervals cause an increase in all the previous studied characters, while irrigation every 12 days significantly reduced it. Spraying the tested rice cultivars by three growth regulators increased all studied characters as compared with control treatment. spraying Giza 179 cultivar with Cytokinin under the different irrigation intervals surpassed Giza177 cultivar and gave the highest value in all the studied characters expect 1000-grain weight followed by ABA. Spraying the two tested cultivars by Cytokinin under irrigation every 12 days which cause water stress relief the harmful of stress in the plant and increase the yield by about 3.2 t/ha specially with Giza179 cultivar as compared with control (without any growth regulator). Moreover, the application of cytokinein extend irrigation intervals from irrigation every 4 days up to irrigation every 8 days without any significant reduction in the yield. these results are benefit for farmers which safer from shortage of irrigation water in their rice field.