No-phase-postselection twin-field quantum key distribution (NPP TF-QKD) protocal is a variant of twin-field quantum key distribution (TF-QKD) protocal. It not only inherits TF-QKD's advantage of overcoming the constraint of a point-to-point QKD link, but also simplifies its security proof. Its practical feasibility has been demonstrated in experiments. However, it has been assumed that the protocol's light source is precisely controllable, but that is unavailable in practical applications due to the drawbacks of practical devices and environmental noises. In this paper, the influence of the light source intensity fluctuation, an example of light source errors, on NPP TF-QKD protocol's performance is discussed both for the symmetrical and asymmetrical channels. The simulation results show that light source errors can decrease the protocol's secure key rate and shorten the transmission distance of NPPTF-QKD protocal.