The invention discloses a phase type electronic measuring tape which comprises a phase-locked loop, a mixer, a microprocessor, a measuring tape, an elastic line and a sampling unit. The phase-locked loop is used for generating two high-frequency signals, namely a principal resonance signal and a local resonance signal. After the mixer directly mixes the principal resonance signal and the local resonance signal, the mixer outputs a low-frequency signal to the sampling unit, and/or the mixer mixes the principal resonance signal which is transmitted to the measuring tape and flows over the measuring tape, the mixer outputs a low-frequency signal to the sampling unit. The sampling unit performs calculation according to the two low-frequency signals and obtains corresponding phase values. The microprocessor calculates the difference between the two phase values and performs calculation by means of a formula for obtaining the length of the to-be-measured tape. The invention further discloses a length measuring method of the phase type electronic measuring tape. The phase type electronic measuring tape and the measuring method thereof have advantages of realizing digitalization of a traditional measuring tape, accurately and quickly reading the length of the pulled-out tape of the measuring tape and improving working efficiency. Furthermore, through software, complicated measuring operations such as area measurement can be finished.