A flashlamp control system of backlight photography and method are provided, which aim at setting aperture grade difference between back scene and fore scene firstly; then supplementing light by utilizing flashlamp, wherein, the step firstly measures light of the main body to be photographed to obtain aperture value of fore scene, and then measures light of the back scene to obtain aperture value of the back scene in a similar way; setting aperture grade difference between the back scene and the fore scene; focusing the main body to work out distance of the main body; reckoning flashlamp index the flashlamp should have to carry through backlight photography according to the aperture value obtained from aperture value difference.