The invention discloses a square ram solidification structure control method for a large numerical control floor type boring machine. The method comprises the following treatment steps that burden isplaced in an induction furnace to be smelted firstly, wherein the burden is composed of following raw materials including, by weight, 27-28 parts of cast iron, 4-5 parts of high-carbon steel, 2-3 parts of a copper-nickel alloy and 5-6 parts of an iron-nickel alloy, the burden is placed in the induction furnace to be heated and smelted into molten iron, and NbC with the weight accounting for 3%-5%of the total weight of the molten iron is added in the smelting process to serve as a grain refining agent; then, the molten iron is poured into a casting die in a center pouring method, preheating isconducted to 200-300 DEG C before casting die pouring, ultrasonic vibration is conducted on the casting die after pouring is finished, the ultrasonic frequency is 30-100 KHZ, the time is 10-15 min, and cavitation is generated in the liquid phase through ultrasonic vibration. According to the square ram solidification structure control method, through the solidification structure control manner, the strength performance of a square ram is improved, and accordingly the usage requirement of the large numerical control floor type boring machine is met.