This study deals with the high temperature (600-135$0^{circ}C$) properties of Kaolin-Phosphate-Water systems. Phosphoric acid, mono aluminum phosphate, mono ammonium phosphate, the mixture of phosphoric acid and mono aluminum phosphate, and the mixture of phosphoric acid and mono ammonium phosphate were used to characterize the M.O.R of the systems with to quantity of phosphates and firing temperature. Firing shrinkage, creeptest, DTA, TGA, and X-ray diffraction patterns were also measured in order to investigate the factors of strengthening. The resules of the experiments are as follows: 1. Linear shrinkage of kaolin-phosphate systems become larger as the firing temperature rise, and generally in the firing temperature of $600^{circ}C$ and 100$0^{circ}C$ the test pieces with phosphate binder show larger then Kaolin-Water system in linear shrinkage and reversed trends were found at 120$0^{circ}C$ and 135$0^{circ}C$. 2. Cold M.O.R. of kaolin-phosphate systems show higher trends in strength as the firing temperature rise. Comparing M.O.R. of test pieces after firing at 135$0^{circ}C$, the mixture of phosphoric acid-mono aluminum phosphate, and phosphoric acid mono ammonium phosphate systems show higher strength than kaolin-mono aluminum phosphate system which widely used, and it shows highest strength when the mole ratio of phosphoric acid and mono ammonium phosphate is 1:1 among the test pieces of kaolin-phosphate systems. 3. The refractoriness of kaolin-phosphate systems are more deteriorated than Kaolin-Water system, and generally, the more addition of phosphate, the lower the refractoriness, however in the range of 4-8% phosphate addition, the difference of the fusion temperature is about 7$0^{circ}C$. 4. The test pieces of T1 and T2 in creep test were same or even higher than kaolin-water system when 6% of phosphoric acid-mono ammonium phosphate was added to kaolin. 5. In case where the phosphoric acid-mono ammonium phosphate was added to kaolin in mole ratio 1:1 the cold M.O.R., after firing at 135$0^{circ}C$, refractoriness and $T_2$ in creep test show better results than kaolin-mono-aluminum phosphate system which is widely used. 6. Phosphoric acid and mono ammonium phosphate react with kaolin in temperature over 100$0^{circ}C$, and it forms aluminum phosphate.