A scheme is presented for producing a high gain recombination x‐ray laser in hydrogen like oxygen by irradiating 7‐&mgr;m‐diam fiber targets with picosecond high‐power laser pulses. The lasing gain coefficient for the O viiiBalmer &agr; transition at 10.2 nm is predicted to be over 100 cm−1. The optimized electron density and temperature are 8.8×1019cm−3and 22 eV, respectively, at the time when the lasing gain reaches its maximum. Significant improvement in gain performance of recombination x‐ray lasers is indicated for picosecond pulse drivers, which might be a route towards saturated recombination x‐ray layers.