The present invention provides a detection device and a method with simplified computing manner A transmitter transmits detection signals to an environment to detect a target. At least a portion of the detection signals are reflected by the target to generate a plurality of reflection signals. A receiver comprises a plurality of receiving units. Each of the receiving units receives the reflection signals to generate a receiving signal. A processing module connected to the receiver includes a conversion unit, an integration unit and a computing unit. The conversion unit converts the receiving signals into transformation signals by a time-domain to frequency-domain transformation. The integration unit integrates the transformation signals into a first integration signal and a second integration signal. The computing unit decomposes the first integration signal and the second integration signal to 1D arrays. The location or the speed of the target is determined by limiting target sites through detection algorithms and a crossed-validation method.