Through to 110 pieces purity transparent and color uniform, 3 x 5 x 7mm blue synthetic spinel made with the flame fusion method on chemical compositions and color parameter measurement the Co2+ content and color changes, clear the influence on Co2+ relationship of blue synthetic spinels’ color appearance. Through LA-ICP-MS to analysis the cause of colorant content, proof that with Co2+, the increase of the content of synthetic spinel will shift blue to purple tone, and C* shows a parabola form with the drop of L*, 700 ppm ~ 900 ppm place in peak. DL* Î (3.55 ~ 76.94) with Co2+ Î (4.59 ppm ~ 1849 ppm) change the largest amount, DC* Î (-9.99 ~ 29.32) next, DH* Î (-20.34 ~ 4.67) compared with before two changes smallest. Co2+ content in 100ppm below, blue color of synthetic spinel with Co2+ content increased changes greatly; 500 ~ 1500 ppm, visually achieve optimal color (C* higher); above 1500ppm, because of the Co2+ overmuch make the color burn cause the overall decline of transparency, the change of L* tends to be gentle, C* decrease obviously. Use Color i5 in standard color measurement instrument lighting source D65, measured the lightness L*, specimen Color a* and b*, chroma C* and tonal angle ho, based on the uniform color space CIE 1976 L*a*b*, in lightness minimum L 9-10 specimen (processing data for standard to 9th), with the help of DE2000 benchmark for calculating formulas, the Color, the color difference train E* by partial correlation analysis card clearly degrees of off color changes L* has certain influence on rDL*×DE* = 0.996, while rDC*×DE*= -0.427, rDH*×DE* = -0.339. Conclusion, the bule color of synthetic spinel because of its Co2+ content changes main influencing L* to contribute to its color appearance.