The invention discloses a ceramsite building block cutting line and a cutting method. The ceramsite building block cutting line comprises a building block conveying and overturning machine, a large cutting machine, a steering conveying and overturning machine and a small cutting machine which sequentially receive conveyed building blocks, wherein the building block conveying and overturning machine is provided with a longitudinal conveying whole section and a longitudinal overturning rear section, and large building blocks are conveyed and longitudinally overturned to the large cutting machine; the large cutting machine is provided with a longitudinal cutting saw blade set, and the large building blocks are longitudinally cut into transversely-arranged middle building block sets; the steering conveying and overturning machine is provided with a longitudinal conveying front section, a transverse conveying middle section and a transverse overturning rear section, the middle building block sets are converted into transverse conveying from longitudinal conveying, and the middle building blocks are transversely overturned to the small cutting machine one by one; and the small cutting machine is provided with a transverse cutting saw blade set, and the middle building blocks are transversely cut into longitudinally-arranged small building block sets. A production line equipment unitis simple in design, the operation mode is simple and reliable, and the cutting efficiency and the cutting quality of the ceramsite building blocks can be well considered.