The invention relates to a method for determining the number of composite insulator pieces for tower insulation, which comprises the following steps of: S1, calculating the number of insulator piecesunder the action of power frequency voltage: if the altitude is less than or equal to 1000 meters, calculating the number n1 of pieces required by each insulator according to a creepage ratio distancemethod; if the altitude is greater than 1000m, obtaining the number n1H of pieces required by each insulator by correcting n1; s2, calculating the number of insulator pieces under the action of lightning overvoltage; s3, calculating the number of insulator pieces under the action of the operation overvoltage; s4, according to the number N of the insulator pieces obtained in the steps S1, S2 and S3, S501, calculating the number nA of the composite insulator pieces in the light and medium pollution areas; calculating the number nB of composite insulators in the heavy pollution area. The numberof the composite insulators can be obtained according to engineering requirements, and therefore the tower insulation requirement is met.