The invention discloses a detection method for radar target long-time accumulation based on a linear frequency modulation continuous wave. The method comprises the following steps: firstly, confirming a to-be-searched space according to a motion model of a to-be-searched target; emitting a linear frequency modulation continuous wave signal, and performing dechirping treatment on a received radar target echo, thereby acquiring the target echo after dechirping; performing FFT (Fast Fourier Transform) on the target echo after dechirping along a fast time dimension, thereby acquiring an echo signal of a slow time-fast time frequency domain; for the echo signal, performing phase-coherent accumulation on each motor parameter vector in the searching space, thereby acquiring evaluation values; and utilizing the evaluation values to judge a threshold. According to the method disclosed by the invention, through long-time phase parameter accumulation, the signal-to-noise ratio after the target accumulation is effectively increased under the condition of limited emitter power, so that the detection performance of the target can be promoted.