A laser energy meter was designed to meet the requirements of laser energy measurement with wide band, high precision and large energy range. The fast-responding thermopile was used as the sensor, and the high-absorptivity carbon nanolene material was coated on the detection surface of thermopile, which realized the wide spectrum absorption. The energy meter had an ultra-wide energy range of 1 mJ~40 J and the high measurement accuracy by using two thermopile detectors arranged on the both sides of the energy meter. The three-dimensional finite element model of the thermal path structure of absorption cavity was established by using the finite element simulation software, and the heating model of different types of laser pulse were simulated. According to the simulation results, the linearity of the detector was corrected, thus the measurement error caused by the nonlinearity between the output electrical signal of the sensor and the measured optical signal was reduced. The calibration experiment of the energy meter was carried out with the standard device of laser energy meter. The measurement results show that the repeatability of the modified laser energy meter is 0.6%, and the linearity is better than 1.1%. The laser energy meter is traceable to the national laser energy benchmark, and the relative extended uncertainty of measurement reaches an excellent level of 2.5% (k=2).