Ultra-short and ultra-intense pulsed lasers (femtosecond lasers) possess extremely high peak power, and hold broad application prospects in laser inertial confinement fusion, high-energy physics, laser micro-processing and other fields. The peak power of femtosecond pulsed lasers is a crucial parameter for evaluating the performance of ultra-short and ultra-intense pulsed laser systems. A peak power measurement method of terawatt-level femtosecond pulsed laser based on the spectral phase coherent direct electric field reconstruction was introduced, along with the composition and working principles of the measurement device. A set of peak power measurement device of terawatt-level femtosecond pulsed laser was constructed, and the sources as well as main factors of measurement uncertainty influencing the measurement results of peak power were analyzed and discussed. The repeatability of the peak power measurement is 2.9%, and the measurement uncertainty reaches 17.6% (k=2), which effectively addresses the issue of peak power measurement of terawatt-level femtosecond laser.