【Objective】An experiment was conducted to observe effects of different fertilizer mixtures on yield of rape seeds in rice growing areas of northern Guangxi in order to find out most economical application rate of fertilizers. 【Method】Various combinations of different amount of N （89.8， 150.0， 179.6， 269.4 and 359.2 kg/ha）， P2O5（60.0， 107.4， 120.0， 240.0 kg/ha）and K2O（60.0， 107.4， 120.0， 240.0 kg/ha）were applied in rice field. Ternary quadratic and unitary quadratic fertilizer effect models were established and optimized on the basis of experimental data to find out the best fertilizer combination.【Result】Treatment No. 13（N3P3K4）produced the highest yield of rapeseed （1911.2 kg/ha)， which increased by 760.1% over control （N0P0K0）. Treatment No.2（N3P3K3） recorded the highest ratio of output to input（15.9） with 3744 Yuan/ha revenue increment. 【Conclusion】According to the fitting equation of fertilizer effect， the N， P2O5 and K2O application rates supporting maximum yield of rapeseed were 239.6，120.3 and 188.9 kg/ha， respectively， and the most economical application rates of N， P2O5 and K2O were 208.9， 98.1 and 173 kg/ha， respectively.