This research aims to study the water hyacinth fiber inside high-density fiber cement board. By using ratio components among cement : fine sand : water hyacinth fiber : water : catalyst accelerated the formations of cement (aluminum sulfate (AI2 (SO4) 3) calcium chloride (CaCl2) sodium silicate (Na2SiO3)) on the ratio 1: 0.2: 0.075: 0.3: 0.03 by weight of total water hyacinth fiber with the steel grating inside. By compressing the mixture cast machine at normal temperature (30 - 35 °C). From the test results the ratio of B4 is the appropriate ratio from the 1st year research result to produce the high-density fiber cement board with the steel grating inside 0.81mm #0.5”. It can pass the TIS 878-2537 standard of Cement Board and good based-on high density and physical properties mechanical properties and thermal insulation. Accelerate the formation of the most suitable cement is calcium chloride (CaCl2).