Abstract: Instability of wellbore is a common problem when drilling in complex strata, which brings great difficulties to drilling. Traditional way of casing can isolate instable wellbore reliably, however, there are some shortcomings:for example, reducing hole-diameter etc. In order to seek a simple, effective way which does not reduce the well diameter for supporting collapsed well section, hot-melt was used in dry hole and polyurethane in hole with water. The paper described the technological principle and lab tests of the two ways in detail. The study indicates that the two kinds of nonmetal sidewall strengthening technology are simple to operate with significant effect and do not reduce the diameter of hole, which have certain application prospect.