The invention discloses a flexible detection device of a numerically controlled machine tool workpiece. The flexible detection device comprises a detection device body, an inner box and conveyor belt fixing devices, wherein an alarm is mounted at the center of the upper part of the front surface of the detection device body; a piece of tempered glass is mounted in the center of the front surface of the detection device body; a power switch is mounted at the lower part of the left side of the front surface of the detection device body; a working switch is mounted at the lower part of the right side of the front surface of the detection device body; the inner box is mounted inside the detection device body; a detection optical combiner is mounted in the center of the upper part of the inner box; a connecting device is mounted in the center of the lower part of the detection optical combiner; an LED display device is mounted in the center of the inner box; a power interface is mounted at the lower part of the right side of the inner box; the conveyor belt fixing devices are mounted at the lower part of the inner box; an inner layer protecting belt is mounted at the outer parts of the conveyor belt fixing devices. According to the flexible detection device, the alarm is mounted at the upper part of the detection device body, so that people can discover problems in time in the detection process.