The present invention relates to a portable pressure swing adsorption (“PSA”) oxygen generator with at least one partition board disposed inside its housing; an oil-free compressor and a control valve assembly are disposed in one of the separated space isolated by at least one fixing board and the at least one partition board; wherein a fan is disposed inclined or vertically on the partition board outside of the isolated space so that air can be blown into the isolated space directly by an air outlet of the fan. The present invention is built in compact structure with small size and light weight to carry and move, and works safely with a choice of three different types of power supplies, which enable the oxygen generator of the present invention to be used more widely than conventional ones.