Carbohydrate-protein interactions on surface and in solution were quantitatively measured by a glycan microarray. Assessing carbohydrate affinities is typically difficult due to weak affinities and limited sources of structurally complex glycans. We described here a sensitive, high-throughput, and convenient glycan microarray technology for the simultaneous determination of a wide variety of parameters in a single experiment using small amounts of materials. Assay systems based on this technology were developed to analyze multivalent interactions and determine the surface dissociation constant (KD,surf) for surface-coated mannose derivatives with mannose binding lectins and antibodies. Competition experiments that employed monovalent ligands in solution yielded KD and Ki values in solution similar to equilibrium binding constants obtained in titration microcalorimetry and surface plasmon resonance experiments.