Weak gradient magnetic field detection is significant. This paper presents a novel micro-fabricated spin-exchange-relaxation-free (SERF) atomic magnetometer for weak gradient magnetic field detection, and the atomic vapor cell is fabricated by micro electro mechanical systems (MEMS) technology. Compared to the single-channel magnetometer, the novel magnetometer's signal-to-noise ratio has increased by 3.63 times. The magnetic field gradient noise of the novel magnetometer reaches 45.33 fToHz-1/2ocm-1 in the frequency range of 8 to 15 Hz, and the novel magnetometer has a CMRR (common mode rejection ratio) of 6.1. At the same time, the relationship between the magnitude of the magnetic field gradient and the peak of the dispersive signal has been verified, which provides an idea for the detection of weak gradient magnetic field.