According to design ideas of the frame of the 170 tons dump truck, and allaying effects on the frame carling from the lift oil cylinder support (LOCS), the lift oil cylinder support of float support structure (LOCSFSS) is designed by optimization technology. Then, hydraulic pressure lifting system is emulated by one-dimensional emulation, and the load curve is gotten during lifting. Based on the load curve, LOCSFSS and the frame carling are all analyzed by explicit dynamics. Afterward, contrasts and analysis are done among float support structure and the other two traditional structures of jointing on bottom steel board structure (JBSBS) and carling structure (CS). Results of that indicate LOCSFSS is obviously better than the other two structures.