发射度是描述束流品质的重要物理量，根据发射度和传输矩阵可以准确计算束流包络和发散角的变化。在考察传统加速器束流发射度测量方法的基础上，提出采用多狭缝法对激光尾场产生的电子束发射度进行测量。采用宽度为20 μm的多狭缝板对发射度为0.05 mm·mrad的激光尾场加速电子发射度进行测量，数值模拟结果表明采用多狭缝法测量的相对误差可以控制在5%以内。并给出了不同狭缝参数对测量精度的影响，模拟结果表明狭缝宽度对发射度测量精度影响最大。狭缝宽度越窄，测量精度越高，反之，则越低。

Emittance is one of the most important parameters for electron beams. Based on the emittance and transfer martrix, beam envelope and angular divergence can be precisely calculated. Considering the limitation of traditional emittance measurement methods, we employed the multi-slit method to measure the emittance of the laser wakefield accelerated electron beams. In our simulation, the slit width was set as 20 μm, the emittance was 0.05 mm·mrad. We have achieved a good consistence with 5% relative error between the measured emittance and the given emittance. We also observed the effect of different parameters on the precisions of measured emittance. It is concluded that the slit width is the most important parameter, the emittance measurement is more accurate with the narrower slit width.