The photon correlation properties of coherently driven atoms strongly coupled with a single-mode cavity and the influence of collective effect on the mean photon number and photon correlation properties in asymmetric coupling are studied in this paper. Under weak pump field excitation, the driven atom can realize the single photon blockade effect, and the overflow photons from the cavity follow the sub-Poisson statistics, showing the anti-bunching state. Additionally, the distance between two atoms affects the dressed energy level. When the couping phase difference of two atoms is greater than 90°, the asymmetric coupling results in strong photon excitation at the central frequency. Due to the resonance effect, the intra-cavity photons exhibit strong bunching behavior. As the intensity of the driving field increases, the number of photons at both sides of the edge gradually rises and the two-photon excitation becomes dominant, which can realize the two-photon blockade, namely that photons appear in pairs. The present system provides a good platform for studying quantum optical phenomena due to collective effects.