A printer may generate striped patterns in the printing images. This is known as jitter, and the jitter is one of most important themes for high quality printing. In a serial printer, jitter is mainly caused by velocity fluctuation of the print-head carriage system. The purpose of this paper is to find out a method for estimating the jitter. An image scanner is used to digitize the print image and a density fluctuation ratio is introduced to valuate the jitter level. It is found that the jitter level depends not only on the carriage’s velocity fluctuation but also on the density of printing image, and it can be estimated by using density velocity curve. The printing experiments in the study have been carried out by way of dye-sublimation transfer, which is usually used for high quality photo printing.