Abstract: Based on the optical fiber loss,solving the modified nonlinear Schrodinger equations,the paper analyses the function affected by GVD and SPM in single-mode optical fiber in negative GVD area. It quantitatively calculates soliton effect picosecond pulse compression induced by optical fiber loss and initial orthochirp. The result shows that initial orthochirp improves the bad affect of compression factors due to the loss and stops the increase of the best optical fiber length. If an appropriate optical fiber length and initial peak power is selected,efficient compression of orthochirp pulse can be attained in single-mode optical fiber.