The invention discloses a preparation method of a radiation heat-proof shield coating on surface of a titanium alloy. The preparation method comprises the steps that firstly, the pre-grinding, acid washing and washing are carried out on the surface of the titanium alloy; secondly, electrolyte is made from sodium hexametasphosphate, sodium silicate, sodium hydroxide, potassium dichromate and water;and thirdly, the titanium alloy is placed in a stainless steel electrolytic cell with the electrolyte, the titanium alloy is used as an anode, the stainless steel electrolytic cell is used as a cathode, micro arc oxidation is carried out on the surface of the titanium alloy to prepare a high radiation heat-proof coating by pulse micro arc oxidation power supply. According to the preparation method of the radiation heat-proof shield coating on the surface of the titanium alloy, micro arc oxidation technology used for preparing, the in-situ growth of a ceramic coating on the surface of the titanium alloy can be realized by controlling the constant pressure in the electrolyte which is made from the sodium hexametasphosphate, the sodium silicate, the sodium hydroxide, and the potassium dichromate, so that the bonding and uniformity of the coating and a matrix are ensured, and the titanium alloy coating with an uniform structure and high radiation heat-proof is prepared.