The objective was to improve the quality and effect of shell breaking on pecan after the firsttime breaking. In order to make up for the shortage of the first shell breaking of pecan and ensure the more effective separation of shell and walnut kernel, a secondary shell breaking method based on centrifugal force impact was proposed for pecan with unsatisfactory shell breaking effect, and a secondary shell breaking machine based on centrifugal force was developed. According to the material characteristics of pecan and various mechanical characteristic parameters required for shell breaking, a mathematical model for the design of the secondary shell breaking mechanism was established, and key structural components such as feeding and shell breaking mechanisms were designed in detail, the key parameters were determined, the whole machine model was established, and the sample machine trial production was completed. The experiment of the sample machine showed that when the water content of pecan was 14.55%~16.35%, and the diameter was 18~22mm (along the seam line direction), the speed of the centrifugal rotating device was 410r/min, the distance between the edge of centrifugal rotating device and the collision wall of conical cylinder was 80mm, and the feeding speed was 200g/s，the effective rate of breakage was larger than 87.85%, the rate of damage to walnut kernel was less than 16.14% and the rate of production exceeded 500kg/h. The accuracy and stability of each sample machine were verified, which met the actual requirements of the current pecan processing industry.