The product is smoke detector, hereinafter called detector. With a unique structure design and an intelligent MCU to process photoelectronic signals, it is provided with dust-proof, mothproof and anti-light interference etc. functions, ensuring the detector stability from design. It reacts very quick to visible smoke released by smoldering fire and flaming fire, and suitable for fire alarm in house, factories, shopping malls, hotels, restaurants, office buildings, teaching buildings, banks, libraries, warehouses, etc.