The invention relates to a method for sieving the frequency of a processor chip, which comprises the following four steps of: obtaining an instruction level function testing vector used for sieving the frequency according to the optimization of the coverage rate of a physical critical path; writing the instruction level function testing vector used for sieving the frequency into a high-speed buffer memory of the processor chip by a scan chain device; and configuring a phase lock ring high-speed clock for the processor chip on an automatic testing instrument, executing the instruction level function testing vector in the high-speed buffer memory to sieve the frequency and evaluating the frequency grade of the processor chip. The method can also comprise the following steps of: obtaining a frequency deviation by sampling the processor chip and carrying out plate level function testing, correcting and calibrating the final frequency of the processor chip. The invention has simple method, low cost and accurate and effective result.