Based on the problem of backward equipment and low automatic control of pretreating of bamboo, this paper proposed to adopt numerical control technology to increase automation based on the processing technique of four-side milling and three-side splitting. This research provided the whole machine structure for four-side milling and three-side splitting of bamboo and designed the numerical control system of four-side planer by PLC according to the technique of four-side milling and three-side splitting. PLC can calculate the corresponding impulse amount to obtain the feed distance after determination of the width and thickness of the bamboo to be processed. The numerically controlled four-side planer possessed functions such as automatic tool-setting, independent processing, single-piece slicing, counting processed pieces and so on. In conclusion, the numerically controlled four-side planer made the pretreating of bamboo more humanized, improved automation of machines and unified the dimension of processed bamboo.