When the nonuniform pulse-train signal is applied to the problem of weak target detection, the traditional long-time integration methods based on FFT are no longer valid. A novel method based on Keystone transform and nonuniform FFT is proposed here to accumulate the echo energy, wherein the former is employed to remove the range walk and the latter realizes the coherent integration of nonuniform pulses. The algorithm's effectivity is further evaluated and verified by numerical simulation experiments.