A new method of emission measurements of optical transition probabilities between two States through stimulated emission phenomena is shown, and the transition probabilities of four lines of argon ion and of three lines of krypton ion are measured. Perturbation spectroscopy is mainly used in our observation and Lamb's rate equations are applied to calculations. At first the ratio of the population densities of the two states of transition is experimentally acquired, and then the transition probability is determined using this ratio of populations. Measured transition probabilities of argon ion are compared with published values and meet in good agreement with them. Measured values of krypton ion are compared with the data of spontaneous emission intensities, and supposed to be reasonable.