The invention provides a lensless microscopic imaging method based on optical projection and a device thereof. The lensless microscopic imaging method comprises the following steps: directly sensitizing and imaging an optically projected image of the object by using a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) or CCD (Charge Coupled Device) image sensor; placing a glass slide between an image sensor and a light source; irradiating the glass slide by a special light source with variable color temperature and variable light intensity to project an object on the glass slide onto the image sensor; controlling the image sensor to conduct exposure imaging for the projected image of the object; and transmitting a digital image produced by the image sensor to an upper computer or other system through a USB interface or 1394 interface. Without the need of optical lens group of the conventional microscope, the device provided by the invention can use the image sensor for digital imaging from the projected image of the object, and can be used for observing micro objects, such as cell, particle and parasites, and has the advantages of small size, compact structure, low cost and direct digitalization, and is convenient in observation, and the like.