Abstract: In order to analysis the stability of a Nanjing slope,a quantitative analysis through test method was carried out.Using test method to reveal change in clay minerals and water content of structural plane influence the strength parameters c、φ and F of rock slope.Some results were present:1) the safety factor was decreased with the increase of clay minerals; it reaches the minimum between 45%~55%; 2) the safety factor was decreased with the increase of water content.Using the particle swarm algorithm analysis the test results、it showed that with the increase in the content of clay minerals,the safety factor of change is non-linear,but always showed a good correlation,the correlation coefficients ranging from small to large; the safe coefficient values and water content showed a negative correlation linear relationship and maintain at a high correlation,the correlation coefficient reached 0.90 or more,it is in line with the general laws of nature.