Core drilling has been widely used in mineral exploration with diamond-impregnated drilling technology. Automation is a critical technology in improving core drilling efficiency and reducing core drilling costs, but there is no complete automation that can control the entire core drilling process. In this paper, an electric drive laboratory drilling system was established using programmable logic controller (PLC) technology. A proportional integration differentiation (PID) control algorithm was developed to achieve closed-loop control of the weight-on-bit (WOB) during the drilling process. Four drilling modes were developed for the drilling system, and their performances were verified by drilling test. A constant-speed mode is proposed as the most suitable mode for the system. The recommended rate of penetration (ROP) of the rock sample and bit used in the experiment was obtained through the power optimization drilling test. The results show that the optimal rotation speed ranged from 700 to 1000 rpm, and the optimal ROP ranged from 2.0 to 2.6 m/h.