Hematology tests, considered as an initial step in patient diagnostic process, require laboratory equipment and technicians which is a time and labor-consuming procedure. Such facilities may be available in a few central laboratories in under-resourced countries. The growing need for low cost and rapid diagnostic tests contributes to point-of-care (POC) medical diagnostic devices providing convenient and rapid test tools particularly in areas with limited medical resources. In the present study, a comprehensive numerical simulation of POC blood cell separation has been modeled using a finite element method. Tag-less separation of blood cells i.e. platelets, red blood cells, and white blood cells was carried out using standing surface acoustic waves (SSAWs) generated by interdigital transducers (IDTs) located at lateral sides of the microfluidic channel. Blood sample intake along with sheath flow was introduced via two symmetrical tilted angle inlets and middle inlet, respectively. Different parameters like wave frequency, wave amplitude, medium flow rate, and microchannel dimensions were analyzed in order to find the best design and optimum condition of blood cell sorting inside the device. Superposition of acoustic radiation force applied by SSAWs accompanied by drag force caused by medium flow drove the blood cells toward different path lines correlated to their size. Red and white blood cells were sorted out through separate locations in the middle outlet and, platelets were sorted out through the side outlets. Each cell then guided to their respected visualization chamber for further image processing analysis. The results of the presented numerical study would be very promising in designing and optimizing the POC blood testing device.