Dawsonite-type compounds of formula MAl(OH) 2CO 3 ( M=Na,K,NH 4) were hydrothermally synthesized. The influences of the composition of starting materials, reaction temperature, acidity of the reaction medium on the formation, morphology and particle size of MAl(OH) 2CO 3 powders were systematically investigated. The experiment results show that increase in the amount of MHCO 3 favors the formation of MAl(OH) 2CO 3 phase with more slender particle morphology. The higher the reaction temperature, the grosser the particle is. It was also demonstrated that the particle size of the MAl(OH) 2CO 3 phase are most uniform when the pH value of reaction system is 10.3 for sodium dawsonite and potassium dawsonite, but it is 9.79 for that of ammonium dawsonite. The thermodynamics of the formation of dawsonite-type compounds have also been analyzed in details.