The pyrotechnic formulation， that emitting purple light by using the synergetic effect of multi flame colorants， was designed and optimized theoretically. Based on the principle of additive color mixing， one purple-light-emitting pyrotechnic formulation containing flame colorants that generating red and blue colors was proposed. The types and contents of different colored light emitters were determined by REAL program. The color coordinates， wavelengths， color purities and chromaticity diagrams of different formulations were calculated by MATLAB program， and then the optimized pyrotechnic composition with purple light was determined. The theoretical results showed that the optimal formulation of purple-light-emitting pyrotechnics was Sr（NO₃）₂/2CuCO₃·Cu（OH）₂/Al/C₆H_9.6O_1.6 with the ratio of 48/32/12/8. The oxygen balance of the formulation was -0.11 g·g^-1 and the colored light emitters were Sr， SrO， SrOH， CuO， CuOH， and CuH， respectively. The purple chromaticity coordinate point was （0.2449，0.1497）. The virtual dominant wavelength of purple light was 446 nm， and the color purity was 0.40. The experimental measurements of the above formulation showed that the chromaticity coordinate point was （0.2425，0.1588）， the virtual dominant wavelength of purple light was 439 nm， and the color purity was 0.44. The purple light was actually produced by the mixing of red light （766 nm） and blue light （418 nm）， with good purple effect. The simulation results are in good agreement with the experimental results. This design method can provide a theoretical basis for the formulation optimization of other colored-light-emitting pyrotechnic compositions with multi flame colorants and the study of related problems.