(DMe-DCNQI) 2 Li is a 14 filled spin-Peierls (SP) system with the SP transition temperature T s p ~65K. Using frequency variable ESR at temperatures enough below T s p , the existence of spin solitons which could arise from domains with finite chain length, is demonstrated. It is also found that T s p is enhanced by hydrostatic pressure and can be reproduced well with Cross-Fisher's relation. Within our knowledge, this is the first example of such good consistency with theory in pressure dependence of T s p . This is probably due to a high one dimensionality of the electronic structure in (DMe-DCNQI) 2 Li, even under high pressures.