Farmers are set to produce over 15 million tonnes which means the country will have a 50% surplus for the year, according to government figures.
The bumper harvest is a result of good rains in January and February.
The extra produce is expected to help to push food prices down, according to agricultural economists.
Food security is a concern for many and in South Africa rising food prices have made life more difficult particularly for the millions of poor and unemployed, says the BBC's Pumza Fihlani.
A drop in the cost of food would be a welcome relief for many households, our correspondent says.
South Africa, along with the rest of the region, is still recovering from the effects of last year's drought that was caused by the El Nino climate phenomenon and led to widespread food shortages.
But, according to the local weather services, the rainfall recorded in January and February this year was more than double the average.
South Africa is expecting to harvest its biggest maize crop in four decades, a year after drought devastated output of the country's staple food.