The molecular environment plays a vital role in regulating the photophysical properties of optoelectronic functional materials. Here, in a series of phenoxazine derivatives with a triazine core and double-branched structures, we found that changes in the surroundings of the triplet chromophore are important to regulate the organic phosphorescence lifetime. The emission lifetime of the 10,10′-(6-methoxy-1,3,5-triazine-2,4-diyl)bis(10H-phenoxazine) (MT) molecule with the strongest interaction between the triplet chromophore reached 325.26 ms, which is 387 times longer than that of the 10,10′-(6-ethoxy-1,3,5-triazine-2,4-diyl)bis(10H-phenoxazine) (ET) molecule with the weakest interaction (0.84 ms). This work indicates that the modulation of the triplet chromophore environment is essential to the performance regulation of organic phosphorescence, which will provide guidance for the development of organic room temperature phosphorescent materials.