In this paper we present a method of observing triplet state transitions of strontium. The intercombination transition is employed to pump the atom population from singlet-state (5s2)1S0 to triplet-state (5s5p)3P1 by a laser at 689 nm. Then 688 nm laser is also employed to divide atom population into the two other triplet-state states (5s5p)3P0 and (5s5p)3PP2. We can obtain the absorption signals of triplet-state transition (5s6s)3S1 → (5s5p)3P0 and (5s6p)3S1 → (5s5p)3P3P2. And these atomic absorption signals can be used for stabilizing the repumping light 679 nm and 707 nm directly to transition line of strontium. This method can be used in the Doppler cooling of strontium atoms.