CMS very forward calorimeter is based on a quartz fibre technology. The calorimeter prototype composed of two longitudinal segments was tested at CERN in 1996, We present the test beam data analysis of this prototype. It was shown that the mean values of responses for pions and electrons of the same energy could be equalised using the appropriate ratio of calibration constants for longitudinal segments. The beam test data were used to simulate the calorimeter response to hadron jets. (C) 1998 Elsevier Science B.V. All rights reserved.