In the present experiments, a new method of atomic spectral measurement using states optical pre-selection was proposed and demonstrated, and the measurement of hyperfine-structures and isotope shifts in the 6s5d 3D --> 6p5d 3F transitions of Ba I was taken as an example. A 791 nm laser was used to excite the different hyperfine transitions 6s6s 1S0 --> 6s6p 3P1 for different isotopes of barium and different hyperfine energy-levels of 6s5d 3D2 for these isotopes were populated by the 6s6p 3P1 --> 6s5d 3D2 spontaneous radiations, then the corresponding fluorescence spectra of 6s5d 3D2 --> 6p5d 3F2 transitions excited by another 778 nm laser were recorded. Comparing of these spectra, 22 lines were recognized and the hyperfine-structure constants of 6s5d 3D2 and 6p5d 3F2 of 135Ba and 137Ba were evaluated consequently while the isotope shifts of these transitions were also determined.