In this paper, we report a method of printing uniform protein lines on glass slides by using UV-treated flat PDMS stamps. Unlike traditional microcontact printing (μCP) which requires microstructured PDMS stamps, this μCP method only requires a flat PDMS stamp, an UV lamp and a number of straight needles. Our results show that lines of bovine serum albumin (BSA), immunoglobin (IgG), anti-biotin, anti-human IgG and anti-mouse IgG can be printed evenly on glass slides by using this μCP method. We also demonstrate that the printed protein lines are suitable for applications such as microfluidic immunoassays.