In laser metal deposition, fixed process parameters are usually used during the deposition, which easily leads to heat accumulation. In order to reduce the oxidation of titanium alloys caused by heat accumulation during the deposition, a closed-loop control system of molten pool temperature with variable laser power between layers is proposed. For the deposition of TC4 titanium alloy, a PI-controller is designed to control the actual temperature of the molten pool with laser power as input variable. The experimental results indicate that the actual temperature of the molten pool can reach the expected value using PI-controller. The surface of the deposited part is bright silvery white without oxidation. Compared with the deposited part with fixed laser power, the closed-loop controlled deposition block has smaller β columnar crystal and more uniform width, and the microhardness does not increase at the top position. This system provides a new method to control the temperature of the molten pool and provides technical support for the continuous deposition of titanium alloy in an open environment.