The Ocean Color Imager is an electro-optic remote sensing instrument to be flown on the ROCSAT-1 satellite, scheduled to be launched in January 1999. It is a push-broom type spectral-radiometer with 702 km swath width and 800 m resolution for measuring radiances of water-leaving from ocean surfaces and atmospheric scattering in six visible and near infrared bands. The OCI's missions, architecture, function, and pre-launch performance test results are described here.