In this paper, a magnetooptic chip was prepared on Si wafer by combinatorial Ga+ implantation into ion sputtered Co7Ag93 film. The surface morphology of each unit of the chip was detected by AFM, while their Kerr effect was measnred by MOKE equipment. It is observed that the maximum Kerr rotation (MKR) occurs when thc incident photon energy is around 3.8-3.9 eV. Summarization of MKR wer sus implanted Ga+ dose shows that the MKR enhancement by Ga+ implantation can be characterized as incubation, enhancement and saturation regions. Considering the mutual solubility and surface morphology transition after annealing, it is suggested that Ga+ tends to form CoCa and/or CoCa3 intermetallic compounds. Before the formation of CoGa3 compounds, no apparent MKR enhancement could be obserwed. While when the surface is half occupied by forest-like CoCa3 compounds, MKR enhancement will be saturated. By comparison of the maximum Kerr rotation with the cone areal density, it can be induced that not only the bulk concentration and structure, but also the surface morphology plays an important role in magnctooptic Kerr effect.