The oxide/nitride passivation and the flip-chip package technology are developed for the perovskite solar cells. The heat resulting from the physical vapor deposition decomposes the active perovskite layer and degrades the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si-nitride passivation processed by plasma-enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1%. It is because that the plasma-enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency-decay curves of the flip-chip packaged perovskite solar cells, the characteristic time of the reliability-tested solar cell can be calculated to be 145.8, 390.7, and 4864 h for air-ambient, glove chamber, and water-ambient tests, respectively. It is concluded that the concentration of O2(g) in the reliability test ambient is the root cause for the efficiency degradation of the perovskite solar cells. The low mobility of O2(g) under the water-ambient reliability test results in the low probability of the adsorption of O2(g) on the surface of the flip-chip package, which is the key factor for the least efficiency degradation of the perovskite solar cells among the three reliability tests.