Abstract: A portable X-ray Fluorescence Spectrometer can be used for quantitative field analysis with the advantages of rapidity and multi-elemental analysis, while possessing broad application prospects for exploration of cobalt-rich crust resources. However, there also some capacity for improving the resolution and stability of the instrument, and the applications of in-situ analysis need to be developed. Based on the features of a relatively high content of target elements, a method has been introduced for the determination in field of Mn, Fe, Co, Ni, Cu and Zn in cobalt-rich crusts collected from the Pacific Ocean by portable X-ray Fluorescence Spectrometer (AFS) coupled with a directly pressed powder sample preparation technique. The reliability of the method is discussed. The proposed method has been validated by analyzing certified reference materials, the relative standard deviations being 0.2%-3.0% and accuracies of 92.9%-107.6%. The described method was also assessed by field detection and laboratory testing, and good consistencies were obtained for the elements of interest except for low content of Cu, which would meet the need of testing quality management for exploration of cobalt-rich crusts resources. The data of in-situ analysis was evaluated by comparing with that obtained from AFS after sample preparation, which show that the results from in-situ analysis are lower for Mn, Fe, Co and Ni with accuracies of 68%-100%. The method has been proved to be simple and effective, which is appropriate for fast analysis in preliminary evaluation of cobalt-rich crusts resources.