A method for managing handheld device power consumption, comprising the following steps: calculating an operating frequency needed by a function currently operated by a handheld device; and setting a system clock of the handheld device according to the operating frequency; wherein the step of setting the system clock of the handheld device according to the operating frequency further comprises: step 1: selecting a NO value according to NO= 2 OD[1: 0], where OD[1: 0] is a frequency division coefficient of an output clock; step 2: estimating the value of NF/NR according to NF NR = Fout × No Fin, where NR=R[4; 0]+1 is an input frequency division parameter, NF=F[5: 0]+1 is a feedback parameter, Fout is an output frequency of the system clock, R[4: 0] is an input frequency division coefficient of a reference clock, F[5; 0] is a frequency division coefficient of a feedback clock, Fin is an input frequency and Fin is a constant value; and step 3: determining whether the output frequency obtained through a calculation is equal to the operating frequency; if the output frequency is equal to the operating frequency, configuring the handheld device with the NO, NF and NR values to which the output frequency corresponds; if the output frequency is not equal to the operating frequency, executing step 1 till there is not an unselected NO value, finding an output frequency closest to the operating frequency and configuring the handheld device with the NO, NF and NR values to which the closest output frequency corresponds when there is not an unselected NO value. calculating an operating frequency needed by a function currently operated by a handheld device; and setting a system clock of the handheld device according to the operating frequency; wherein the step of setting the system clock of the handheld device according to the operating frequency further comprises: step 1: selecting a NO value according to NO= 2 OD[1: 0], where OD[1: 0] is a frequency division coefficient of an output clock; step 2: estimating the value of NF/NR according to NF NR = Fout × No Fin, where NR=R[4; 0]+1 is an input frequency division parameter, NF=F[5: 0]+1 is a feedback parameter, Fout is an output frequency of the system clock, R[4: 0] is an input frequency division coefficient of a reference clock, F[5; 0] is a frequency division coefficient of a feedback clock, Fin is an input frequency and Fin is a constant value; and step 3: determining whether the output frequency obtained through a calculation is equal to the operating frequency; if the output frequency is equal to the operating frequency, configuring the handheld device with the NO, NF and NR values to which the output frequency corresponds; if the output frequency is not equal to the operating frequency, executing step 1 till there is not an unselected NO value, finding an output frequency closest to the operating frequency and configuring the handheld device with the NO, NF and NR values to which the closest output frequency corresponds when there is not an unselected NO value. step 1: selecting a NO value according to NO= 2 OD[1: 0], where OD[1: 0] is a frequency division coefficient of an output clock; step 2: estimating the value of NF/NR according to NF NR = Fout × No Fin, where NR=R[4; 0]+1 is an input frequency division parameter, NF=F[5: 0]+1 is a feedback parameter, Fout is an output frequency of the system clock, R[4: 0] is an input frequency division coefficient of a reference clock, F[5; 0] is a frequency division coefficient of a feedback clock, Fin is an input frequency and Fin is a constant value; and step 3: determining whether the output frequency obtained through a calculation is equal to the operating frequency; if the output frequency is equal to the operating frequency, configuring the handheld device with the NO, NF and NR values to which the output frequency corresponds; if the output frequency is not equal to the operating frequency, executing step 1 till there is not an unselected NO value, finding an output frequency closest to the operating frequency and configuring the handheld device with the NO, NF and NR values to which the closest output frequency corresponds when there is not an unselected NO value.