Zhuge Liang was impressed by Ma Su's knowledge and strategies. But Liu Bei warned him until his death, that Ma Su was not as intelligent as he seemed. Nonetheless, Zhuge Liang continued to hold large chunks of Ma Su and deeply involved him in his plans. When Zhuge Liang prepared his Northern Campaigns against the Wei, He moved south to conquer the Nanzhong region first. Ma Su then developed a plan to capture Nanman king Meng Huo seven times during the southern campaign. After Meng Huo and Zhurong was surrendered, they are becomes a vassals of Shu. When Ma Su advised Zhuge Liang to spread the false rumors about Sima Yi, because Cao Rui suspected of the man. Zhuge Liang did as advised, and Sima Yi was fired. many considered generals Wei Yan and Wu Yi the most appropriate commanders, but Zhuge Liang entrusted Ma Su instead.
However, Ma Su met Wei General Zhang He at the Battle of Jieting, but was surrounded by him and defeated. Ma Su was deemed by Zhuge Liang to hold major responsibility for the failure of the first Northern Expedition. Ma Su's wife and children were said to have been well taken care of by Zhuge Liang after Ma Su's death.
- His height in Kessen II is 170 cm (5'7").