In this paper, Ni-Sn-P ternary alloy coating was prepared by the electroless depositing technique. Effects of tannic chloride, reductant and pH value of the bath on the coating were studied. And, erosion behavior of the coating in the 3.5g dm-1 sodium chloride solution was also investigated. The results show that the electroless deposited Ni-Sn-P ternary alloy is amorphous. The deposition rate and the tin content in the coating increase, but the phosphorus content in the coating decreases with increasing the stannic chloride and sodium hypophosphite contents in the bath. The deposition rate increases with the pH value of the bath in the range of 3 to 6. Mass loss of the coating increases with increasing the erosion time and the flow velocity of erosion solution, which has its maximum value as the coating impacted at an angle of 60°.