In order to study the influence of time delay on the stability of traffic flow, this paper constructs an analysis model of the mixed traffic flow stability of human-driven vehicles and intelligent connected vehicles considering time delay. Firstly, the proportional relationship and delay value of different types of car-following modes in mixed traffic flow are analyzed and determined. Then, on this basis, different car-following parameters and time delay values are used to distinguish the car-following modes. The linear stability of the mixed traffic flow is derived from this condition. Finally, taking the intelligent driver model(IDM) as an example, the influence of the penetration rate of intelligent connected vehicles, the driver's perception delay and the vehicle communication delay on the stability of the mixed traffic flow are discussed based on the numerical experiments. The results show that intelligent connected vehicles can improve the linear stability of the mixed traffic flow, while the driver's perception delay and the vehicle communication delay are harmful to the balance of the mixed traffic flow system. Compared with human-driven vehicles, automated vehicles (AVs) still have a small effect on the stability of mixed traffic flow, which shows that intelligent connected vehicles can alleviate the interference to the mixed traffic flow system to a certain extent.