In order to find out the effect of a plant growth regulating hormone, commonly called as 2, 4, 5-TP, for checking the resisting energy against falling of grain of Indica-Japonica species rice, an experiment was conducted with five levels of consistency (5,10, 15, 20, 25 ppm) and with four levels of spray timing (8, 17, 27, 34 DAH). Ten applications were made for measuring the resisting energy of rice heads sampled from every lot of treatments. Followings are the results; 1.The rice heads applied with 2, 4, 5-TP showed remarkably higher resisting energy against falling of grain comparing with those from the control plot. 2.The highest average value of the resisting energy was found as 83, 326 erg per grain on the plots of 8 DAH spray. 3.The general tendency was found that the more the timing of spraying was early, the more the consistency was lean. 4.A regression equation for expressing the peak resistance versus the timing was derived by means of least squares as follow; C=0. 00042D$^3$-0. 012D$^2$+0. 267D+8. 394 5.No significant differences were found among the values of weight per 1, 000 grains neither among moisture content.