When atoms are exposed to strong femtosecond laser fields, there is a high probability that the electrons in atoms can be excited to the Rydberg states with very high principal quantum numbers and large orbitals, in addition to processes such as multiphoton ionization and tunneling ionization. This highly excited state of the atom is very stable in the ultrashort strong laser pulse and is closely related to many other phenomena in the strong field, such as neutral particle acceleration, multiphoton Rabi oscillations, near-threshold harmonic radiation. It has become one of the research hotspots in the field of strong-field ultrafast physics in the last decade. Among these studies, the mechanism of the generation of Rydberg atoms in strong laser fields, the modulation of Rydberg states by lasers, and the strong-field ionization process and stability of Rydberg states are the main issues of interest.This review provided an overview of the generation mechanisms of the Rydberg states driven by strong laser fields. There are two mechanisms for strong field Rydberg state excitation. One is multiphoton resonance excitation and the other is Frustrated Tunneling Ionization (FTI) excitation. The dependence of the yield of the Rydberg state atoms on the laser ellipticity is usually considered to be an important basis for determining whether the Rydberg state atom generation mechanism is multiphoton resonance excitation or frustrated tunneling ionization. However, this judgment is not reliable. As shown in this review, for multiphoton resonance excitation, the yield of Rydberg state atoms also decreases rapidly with increasing laser ellipticity. In contrast, in the nonadiabatic tunneling ionization region, the yield of Rydberg state atoms in FTI does not always decrease with increasing laser ellipticity, instead, it shows an abnormal increase in the yield. There is no clear boundary between these two mechanisms.This review focused on a variety of interference phenomena during the Rydberg-state excitation of atoms driven by strong laser fields, which are manifested as oscillations of the Rydberg state atomic yield with laser intensity. These interference phenomena are classified into three categories according to the magnitude of the as-Stark shift corresponding to the laser intensity interval of the oscillation period. The first category is the interference with an oscillation period of one photon energy. In multiphoton resonance excitation images, this interference can be understood as channel closing. In tunneling images, it can be understood as coherent recapture, wherein the electrons tunneling ionize at different laser cycles, are recaptured, and interfere, giving rising to the laser-intensity-dependent oscillation of the excitation yield. The second category is the interference with oscillation periods much larger than one photon energy, which usually appears in the long wavelength region. This type of oscillation is explained as the interference of the tunneling electron recaptured at different returns. The third category is the interference with oscillation period much smaller than one photon energy, due to the interference of the excitation during the rising and falling edges of the laser pulse, i.e., the dynamic interference. These interference phenomena provide the dynamic information of the strong-field excitation process of the Rydberg-state atom.In this review, the ionization processes of excited atoms in strong laser fields are also presented, in particular, the circular dichroism of ionization of the Rydberg atoms driven by circularly polarized laser fields. Because of this circular dichroism, the Rydberg state can be considered as the simplest chiral system, which is important for one to explore the chirality of molecules. In addition, the circular dichroism of Rydberg state atoms is also important for the preparing and detecting high-purity single ring current states at ultrafast time scales and the generation of spin-polarized electron pulses.