The invention relates to a weak alkaline light magnesia olivine brick and a manufacturing method thereof. It is made of olivine sand, magnesia, coke, charcoal and pulp waste liquor in proportion by weight. Magnesium brick manufacturer's manufacturing methods are as follows: adding olivine sand, magnesia sand, coke and charcoal granules into dry mixing machine, then adding pulp waste liquid, wet mixing, and then adding olivine sand and magnesia fine powder to mix; Magnesium-zirconium brick adds the mixed material into the mould, and presses it into a blank on the friction machine; the blank is dried naturally at 25-35 degrees Celsius for more than 24 hours, and fed into the blank. Drying kiln drying, the dried body into the tunnel kiln, firing; firing products after cutting, grinding and forming. Because of its weak alkalinity, the magnesia olivine brick of the invention avoids acid-alkali reaction with the working lining alkaline brick caused by high temperature, improves the service life of the backup light heat insulation brick of the alkaline working lining brick, thereby reducing its damage degree and speed, and can still be used at a temperature of 1540 degrees or even higher.