Coal and gas outburst is a violent disaster driven by released energy from gas desorption. The initial expansion energy of released gas (IEERG) is a new method to predict coal and gas outburst. In this paper, an instrument for IEERG measurement was developed. Compared with previous setups, the new one which is equipped with three convergent nozzles and quick-release mechanism gets improved in data acquisition and gas sealing and releasing performance. To comprehensively know the effect of gas pres-sure, particle size, and nozzle area on IEERG, a series of experiments were carried out with this new setup. The variable control test results indicated that the gas pressure-IEERG curves remain the linear trend and the particle size-IEERG curves maintain the negative exponential trend for nozzle areas at 1.13, 2.26, and 3.39 mm2, respectively. The increase in nozzle area leads to deceases in value of IEERG and absolute value of slope of fitting curves in each test. In addition, the orthogonal experiment showed that the influence of gas pressure, nozzle area, and particle size on IEERG decreases in turn. Only gas pressure had a marked impact on IEERG. This work offers great importance in improving the accuracy of prediction of coal and gas outburst.