This paper examines the parametric analysis of a solar water-air heater by using transient approach. In this study, the solar water-air heater is the conventional flat-plate air heater combined with water heat storage. When the absorber plate absorbs solar radiation, water will then be heated up. Air temperature can then be increased by extracting heat from water. Heated air is outcome of this collector which is used for drying application afterward. The proposed collector could generate hot air longer than a conventional flat-plate air heater. Simulation computer program is employed to predict four variables by using designed parameters. These variables are investigated in this paper including temperatures of absorber plate, water, air pipe, and air flow as well as the effective heat gained and heater efficiency. The effect of designed parameters i.e. mass flow rate, water depth, and air tube length per collector area are studied. Results are graphically shown. This research can improve a drying system because drying still can operate at night without solar radiation.