Abstract: 78.3% of arable land in Mingqing, Fujian is deficient in magnesium. In order to explore the effects of agriculture-used magnesium hydroxide on the yield of cabbage and late rice and soil magnesium content, field experiments includes 5 different levels of application rates of magnesium were conducted, and magnesium hydroxide fertilizer was basal applied, cabbage and late rice were chosen as materials, which had large cultivated area and sensitive to magnesium. The results showed that the application of magnesium hydroxide increased rice chlorophyll content in tillering stage and full heading stage. Under proper dosage, the application of magnesium hydroxide could increase the yield of cabbage and late rice, and the best application amounts were 225 and 120 kg/hm², which could increase economic benefit 12423.9 and 1410 yuan/hm², and the increase rates were 12.7% and 9.1% , respectively. The late rice yield decreased significantly when the application amount of magnesium hydroxide was above 120 kg/hm². The contents of available magnesium in cabbage and late rice soil under the highest yield magnesium hydroxide application level increased 14.3 and 11.3 mg/kg, respectively. Late rice was more sensitive to magnesium than cabbage under the same soil available magnesium level, too much available magnesium could lead to the reduction of yield. Proper application of magnesium hydroxide in cabbage and late rice could increase yield and soil available magnesium amount and promote the balance of soil nutrient.