The invention discloses a gravity casting machine with a detector. The machine is characterized in that the machine comprises a rack mechanism, a moving die mechanism, a machine detecting mechanism and a control mechanism; an air tap is formed in the lower portion of the machine detecting mechanism; a rotating cylinder of the machine detecting mechanism is adopted to rotate a mechanical arm to a position under a product after a lower die disengages from the product, a lifting cylinder is adopted to make a product frame get close to the product, and upper and lower cylinders are adopted to make a detecting frame carry a detection head of the detector to abut on a must-detected position closely where a shrinkage porosity is prone to be formed for touch detection, so that online manual piece picking detection is replaced; when an adopted online machine detecting mechanism receives a disqualification signal from detection, the product frame is pushed by a telescopic cylinder to convey an unqualified product which passes through an upper stripping die to another place, so that intelligent classifying is achieved; when the mechanical arm rotates to be under the product, grit blasting and cooling are conducted on the lower die by the air tap to replace online manual work of residual grit cleaning by an air gun and lower die cooling; an original gravity casting machine is adopted for transformation, so that input is more saved, waste is reduced, and the product cost is lowered.