Context : We present results of an extensive world-wide observing campaign of MN Draconis .

Aims : MN Draconis is a poorly known active dwarf nova in the period gap and is one of the only two known cases of period gap SU UMa objects showing the negative superhumps .
Photometric behaviour of MN Draconis poses a challenge for existing models of the superhump and superoutburst mechanisms .
Therefore , thorough investigation of peculiar systems , such as MN Draconis , is crucial for our understanding of evolution of the close binary stars .

Methods : To measure fundamental parameters of the system , we collected photometric data in October 2009 , June-September 2013 and June-December 2015 .
Analysis of the light curves , O - C diagrams and power spectra was carried out .

Results : During our three observational seasons we detected four superoutburts and several normal outbursts .
Based on the two consecutive superoutbursts detected in 2015 , the supercycle length was derived P _ { sc } = 74 \pm 0.5 days and it has been increasing with a rate of \textit { \ . { P } } = 3.3 \times 10 ^ { -3 } during last twelve years .
Based on the positive and negative superhumps we calculated the period excess \varepsilon = 5.6 \% \pm 0.1 \% , the period deficit \varepsilon _ { - } = 2.5 \% \pm 0.6 \% , and in result , the orbital period P _ { orb } = 0.0994 ( 1 ) days ( 143.126 \pm 0.144 min ) .
We updated the basic light curve parameters of MN Draconis .

Conclusions : MN Draconis is the first discovered SU UMa system in the period gap with increasing supercycle length .