Star formation rates in distant radio galaxies are crucial forunderstanding the evolution of galaxies. Most processes at works inthese targets observed at the most remote epochs are directly or notrelated to primeval sources of star formation: interplays of starburstsand AGNs, interactions of radio jets with environmental clouds. coolingflows, metal enrichment and dust distributions. Signatures of typicalstar formation (emission line ratios, equivalent widths, stellar continua)are observed in distant galaxies. However in most cases, they are superimposedto signatures of other processes (shocks, AGN light scattering).in particular at high z with the decrease of angular resolutionand surface brightness. A larger variety of environmental components(lobes, jets, clouds and nucleus) simultaneously contribute to the globalemission. So that to separate the varions emission processes becomesrapidly essential with higher distances. The 3D spectroscopy is uniqueto disentangle the various physical processes triggering star formationat high redshifts. Shocks and regions photoionized by the central AGNare identified from their typical features and may be localized in the variouszones of the radio galaxy extended to its environment. We presentresults of a long term observationnal prograin with the successive IntegralField Units (IFU) TIGER and OASIS at CFHT. The presentsample consists of three galaxies of increasing z: 3C 171 {z = 0.238),3C 435A (z = 0.470) and 4C 41.17 (z = 3.8). Line ratios, continua andvelocity fields are locallv measured. Interpretations of emission line ratios,velocity fields, equivalent widths, are possible with a coupled codebased on CLOUDY and MAPPINGSIII results, as proposed by Moyet al. (2000, 2001). Stellar and nebular continua are interpretcd withthe help of our evolutionary synthesis model PEGASE2. Ail modelstake into account metallicity effects.