Potassium dihydrogen phosphate (KDP), ammonium dihydrogen phosphate (ADP), and K(x)A(1-x)DP (x=0-1 step 0.1) crystals were fabricated on KDP and ADP seed crystals by dropping a KADP solution. The KADP solution, with a temperature of 18 degrees C, was dropped onto a substrate at a temperature of 35 degrees C. The KADP crystals were subsequently deposited onto the substrate because of the different solubilities of the dropped solution and the solution at the substrate. The composition of the KADP crystal could be controlled by changing the precursor solution ratio of KDP and ADP. From this simple process, the K(x)A(1-x)DP (x=0-1, step 0.1) crystals were obtained.