Summary: The knotting probability is defined by the probability with which an \(N\)-step self-avoiding polygon (SAP) with a fixed type of knot appears in the configuration space. We evaluate these probabilities for some knot types on a simple cubic lattice. For the trivial knot, we find that the knotting probability decays much slower for the SAP on the cubic lattice than for continuum models of the SAP as a function of \(N\). In particular the characteristic length of the trivial knot that corresponds to a ‘half-life’ of the knotting probability is estimated to be \(2.5 \times 10^5\) on the cubic lattice.