The invention discloses a method for purging and cleaning a spiral tube heat exchanger by using compressed air. The method comprises the following steps: (1) judging the pipe blowing feasibility of provided compressed air according to whether the pipe blowing coefficient at each measured part of single blown pipe is greater than 1, and ensuring that the pipe blowing coefficient at each measured part of the blown pipe is greater than 1, wherein the spiral tube heat exchanger comprises a plurality of spiral tubes; and (2) repeating the step (1) to obtain mass flow rates of the compressed air required by all the spiral tubes, adding the mass flow rates of the compressed air of all the spiral tubes together to obtain the total amount of required compressed air, and dividing the available compressed air amount by 1.20 times of the total amount of the required compressed air to obtain a value A, wherein when the value A is greater than or equal to 1, the spiral tube type heat exchanger can be purged and cleaned by using the compressed air once, and when the value A is smaller than 1, the quantity of pipe bundles, which are purged and cleaned by using the compressed air once, of the spiral tube heat exchanger, is not greater than A times of the total quantity of the pipe bundles of the spiral tube heat exchanger. According to the method disclosed by the invention, the problem of cleaning the spiral tube heat exchanger is solved.